discovery-api/Overview.html
author Rich Tibbett <richt@opera.com>
Mon, 28 Oct 2013 11:31:42 +1100
changeset 484 608edb43c84d
parent 483 140b6c8d4c18
child 492 2f37e8af951a
permissions -rw-r--r--
Fix minor respec link bugs and other minor editorials
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      Network Service Discovery
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      <p>
        <a href="http://www.w3.org/"><img width="72"
             height="48"
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             alt="W3C"></a>
      </p>
      <h1 class="title p-name"
          id="title"
          property="dcterms:title">
        Network Service Discovery
      </h1>
      <h2 property="dcterms:issued"
          datatype="xsd:dateTime"
          content="2013-10-27T13:29:43.000Z"
          id="w3c-editor-s-draft-28-october-2013">
        <abbr title="World Wide Web Consortium">W3C</abbr> Editor's Draft <time class="dt-published"
            datetime="2013-10-28">28 October 2013</time>
      </h2>
      <dl>
        <dt>
          This version:
        </dt>
        <dd>
          <a class="u-url"
              href=
              "http://dvcs.w3.org/hg/dap/raw-file/tip/discovery-api/Overview.html">http://dvcs.w3.org/hg/dap/raw-file/tip/discovery-api/Overview.html</a>
        </dd>
        <dt>
          Latest published version:
        </dt>
        <dd>
          <a href="http://www.w3.org/TR/discovery-api/">http://www.w3.org/TR/discovery-api/</a>
        </dd>
        <dt>
          Latest editor's draft:
        </dt>
        <dd>
          <a href=
          "http://dvcs.w3.org/hg/dap/raw-file/tip/discovery-api/Overview.html">http://dvcs.w3.org/hg/dap/raw-file/tip/discovery-api/Overview.html</a>
        </dd>
        <dt>
          Editor:
        </dt>
        <dd class="p-author h-card vcard"
            rel="bibo:editor"
            inlist="">
          <span typeof="foaf:Person"><span property="foaf:name"
                class="p-name fn">Rich Tibbett</span>, <a rel="foaf:workplaceHomepage"
             class="p-org org h-org h-card"
             href="http://opera.com/">Opera Software ASA</a></span>
        </dd>
      </dl>
      <p class="copyright">
        <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 2013 <a href=
        "http://www.w3.org/"><abbr title="World Wide Web Consortium">W3C</abbr></a><sup>®</sup> (<a href=
        "http://www.csail.mit.edu/"><abbr title="Massachusetts Institute of Technology">MIT</abbr></a>, <a href=
        "http://www.ercim.eu/"><abbr title=
        "European Research Consortium for Informatics and Mathematics">ERCIM</abbr></a>, <a href=
        "http://www.keio.ac.jp/">Keio</a>, <a href="http://ev.buaa.edu.cn/">Beihang</a>), All Rights Reserved.
        <abbr title="World Wide Web Consortium">W3C</abbr> <a href=
        "http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>, <a href=
        "http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a> and <a href=
        "http://www.w3.org/Consortium/Legal/copyright-documents">document use</a> rules apply.
      </p>
      <hr>
    </div>
    <section id="abstract"
             class="introductory"
             property="dcterms:abstract"
             datatype=""
             typeof="bibo:Chapter"
             resource="#ref"
             rel="bibo:Chapter">
      <h2 aria-level="1"
          role="heading"
          id="h2_abstract">
        Abstract
      </h2>
      <p>
        This specification defines a mechanism for an HTML document to discover and subsequently communicate with
        <abbr title="Hypertext Transfer Protocol">HTTP</abbr>-based services advertised via common discovery protocols
        within the current network.
      </p>
    </section>
    <section id="sotd"
             class="introductory"
             typeof="bibo:Chapter"
             resource="#ref"
             rel="bibo:Chapter">
      <h2 aria-level="1"
          role="heading"
          id="h2_sotd">
        Status of This Document
      </h2>
      <p>
        <em>This section describes the status of this document at the time of its publication. Other documents may
        supersede this document. A list of current <abbr title="World Wide Web Consortium">W3C</abbr> publications and
        the latest revision of this technical report can be found in the <a href="http://www.w3.org/TR/"><abbr title=
        "World Wide Web Consortium">W3C</abbr> technical reports index</a> at http://www.w3.org/TR/.</em>
      </p>
      <p>
        This document represents the early consensus of the group on the scope and features of the proposed
        <abbr title="Application Programming Interface">API</abbr>.
      </p>
      <p>
        This document was published by the <a href="http://www.w3.org/2009/dap/">Device APIs Working Group</a> as an
        Editor's Draft. If you wish to make comments regarding this document, please send them to <a href=
        "mailto:public-device-apis@w3.org">public-device-apis@w3.org</a> (<a href=
        "mailto:public-device-apis-request@w3.org?subject=subscribe">subscribe</a>, <a href=
        "http://lists.w3.org/Archives/Public/public-device-apis/">archives</a>). All comments are welcome.
      </p>
      <p>
        Publication as an Editor's Draft does not imply endorsement by the <abbr title=
        "World Wide Web Consortium">W3C</abbr> Membership. This is a draft document and may be updated, replaced or
        obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in
        progress.
      </p>
      <p>
        This document was produced by a group operating under the <a id="sotd_patent"
           about=""
           rel="w3p:patentRules"
           href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5 February 2004 <abbr title=
           "World Wide Web Consortium">W3C</abbr> Patent Policy</a>. <abbr title="World Wide Web Consortium">W3C</abbr>
           maintains a <a href="http://www.w3.org/2004/01/pp-impl/43696/status"
           rel="disclosure">public list of any patent disclosures</a> made in connection with the deliverables of the
           group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge
           of a patent which the individual believes contains <a href=
           "http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential Claim(s)</a> must disclose
           the information in accordance with <a href=
           "http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section 6 of the <abbr title=
           "World Wide Web Consortium">W3C</abbr> Patent Policy</a>.
      </p>
    </section>
    <section id="toc">
      <h2 class="introductory"
          aria-level="1"
          role="heading"
          id="h2_toc">
        Table of Contents
      </h2>
      <ul class="toc"
          role="directory"
          id="respecContents">
        <li class="tocline">
          <a href="#introduction"
              class="tocxref"><span class="secno">1.</span> Introduction</a>
        </li>
        <li class="tocline">
          <a href="#conformance"
              class="tocxref"><span class="secno">2.</span> Conformance</a>
          <ul class="toc">
            <li class="tocline">
              <a href="#dependencies"
                  class="tocxref"><span class="secno">2.1</span> Dependencies</a>
            </li>
          </ul>
        </li>
        <li class="tocline">
          <a href="#terminology"
              class="tocxref"><span class="secno">3.</span> Terminology</a>
        </li>
        <li class="tocline">
          <a href="#security-and-privacy-considerations"
              class="tocxref"><span class="secno">4.</span> Security and privacy considerations</a>
          <ul class="toc">
            <li class="tocline">
              <a href="#security-considerations-for-api-implementations"
                  class="tocxref"><span class="secno">4.1</span> Security considerations for <abbr title=
                  "Application Programming Interface">API</abbr> implementations</a>
            </li>
            <li class="tocline">
              <a href="#privacy-considerations-for-api-implementations"
                  class="tocxref"><span class="secno">4.2</span> Privacy considerations for <abbr title=
                  "Application Programming Interface">API</abbr> implementations</a>
            </li>
            <li class="tocline">
              <a href="#additional-api-implementation-considerations"
                  class="tocxref"><span class="secno">4.3</span> Additional <abbr title=
                  "Application Programming Interface">API</abbr> implementation considerations</a>
            </li>
          </ul>
        </li>
        <li class="tocline">
          <a href="#requesting-networked-services"
              class="tocxref"><span class="secno">5.</span> Requesting networked services</a>
          <ul class="toc">
            <li class="tocline">
              <a href="#methods"
                  class="tocxref"><span class="secno">5.1</span> Methods</a>
            </li>
            <li class="tocline">
              <a href="#error-handling"
                  class="tocxref"><span class="secno">5.2</span> Error Handling</a>
            </li>
          </ul>
        </li>
        <li class="tocline">
          <a href="#obtaining-networked-services"
              class="tocxref"><span class="secno">6.</span> Obtaining networked services</a>
          <ul class="toc">
            <li class="tocline">
              <a href="#attributes"
                  class="tocxref"><span class="secno">6.1</span> Attributes</a>
            </li>
            <li class="tocline">
              <a href="#methods-1"
                  class="tocxref"><span class="secno">6.2</span> Methods</a>
            </li>
            <li class="tocline">
              <a href="#events"
                  class="tocxref"><span class="secno">6.3</span> Events</a>
            </li>
          </ul>
        </li>
        <li class="tocline">
          <a href="#communicating-with-a-networked-service"
              class="tocxref"><span class="secno">7.</span> Communicating with a networked service</a>
          <ul class="toc">
            <li class="tocline">
              <a href="#attributes-1"
                  class="tocxref"><span class="secno">7.1</span> Attributes</a>
            </li>
            <li class="tocline">
              <a href="#states"
                  class="tocxref"><span class="secno">7.2</span> States</a>
            </li>
            <li class="tocline">
              <a href="#events-1"
                  class="tocxref"><span class="secno">7.3</span> Events</a>
            </li>
          </ul>
        </li>
        <li class="tocline">
          <a href="#service-discovery"
              class="tocxref"><span class="secno">8.</span> Service Discovery</a>
          <ul class="toc">
            <li class="tocline">
              <a href="#zeroconf-mdns-dns-sd"
                  class="tocxref"><span class="secno">8.1</span> Zeroconf (<abbr title="Multicast DNS">mDNS</abbr> +
                  <abbr title="Domain Name System">DNS</abbr>-<abbr title="Service Discovery">SD</abbr>)</a>
            </li>
            <li class="tocline">
              <a href="#simple-service-discovery-protocol-ssdp"
                  class="tocxref"><span class="secno">8.2</span> Simple Service Discovery Protocol (<abbr title=
                  "Simple Service Discovery Protocol">SSDP</abbr>)</a>
            </li>
            <li class="tocline">
              <a href="#discovery-and-launch-protocol-dial"
                  class="tocxref"><span class="secno">8.3</span> Discovery and Launch Protocol (<abbr title=
                  "Discovery and Launch Protocol">DIAL</abbr>)</a>
            </li>
            <li class="tocline">
              <a href="#network-topology-monitoring"
                  class="tocxref"><span class="secno">8.4</span> Network Topology Monitoring</a>
            </li>
          </ul>
        </li>
        <li class="tocline">
          <a href="#events-summary"
              class="tocxref"><span class="secno">9.</span> Events Summary</a>
        </li>
        <li class="tocline">
          <a href="#garbage-collection"
              class="tocxref"><span class="secno">10.</span> Garbage collection</a>
        </li>
        <li class="tocline">
          <a href="#use-cases-and-requirements"
              class="tocxref"><span class="secno">11.</span> Use Cases and Requirements</a>
        </li>
        <li class="tocline">
          <a href="#examples"
              class="tocxref"><span class="secno">A.</span> Examples</a>
        </li>
        <li class="tocline">
          <a href="#acknowledgements"
              class="tocxref"><span class="secno">B.</span> Acknowledgements</a>
        </li>
        <li class="tocline">
          <a href="#references"
              class="tocxref"><span class="secno">C.</span> References</a>
          <ul class="toc">
            <li class="tocline">
              <a href="#normative-references"
                  class="tocxref"><span class="secno">C.1</span> Normative references</a>
            </li>
            <li class="tocline">
              <a href="#informative-references"
                  class="tocxref"><span class="secno">C.2</span> Informative references</a>
            </li>
          </ul>
        </li>
      </ul>
    </section>
    <section class="informative"
             id="introduction">
      <h2 aria-level="1"
          role="heading"
          id="h2_introduction">
        <span class="secno">1.</span> Introduction
      </h2>
      <p>
        <em>This section is non-normative.</em>
      </p>
      <p>
        This specification defines the <a href="#navigatornetworkservice"><code>NavigatorNetworkService</code></a>
        interface to enable Web pages to connect and communicate with Local-networked Services provided over
        <abbr title="Hypertext Transfer Protocol">HTTP</abbr>. This enables access to services and content provided by
        home network devices, including the discovery and playback of content available to those devices, both from
        services such as traditional broadcast media and internet based services as well as local services. Initial
        design goals and requirements provided by the <a href="http://www.w3.org/2011/webtv/"><abbr title=
        "World Wide Web Consortium">W3C</abbr> Web &amp; TV interest group</a> are documented in [<cite><a class=
        "bibref"
           href="#bib-hnreq">hnreq</a></cite>].
      </p>
      <p>
        Using this <abbr title="Application Programming Interface">API</abbr> consists of requesting a well-known
        service type, known by developers and advertised by Local-networked Devices. User authorization, where the user
        connects the web page to discovered services, is expected before the web page is able to interact with any
        Local-networked Services.
      </p>
      <p>
        A web page creates a request to obtain connectivity to services running in the network by specifying a
        well-known discovery service type that it wishes to interact with.
      </p>
      <p>
        The user agent, having captured all advertised services on the network from the <a href=
        "#dfn-service-discovery-mechanisms"
           class="internalDFN">service discovery mechanisms</a> included in this recommendation, attempts to match the
           requested service type to a discovered service according to the processing described herein. Only
           Local-networked Services that pass a <a href="#dfn-preliminary-cors-check"
           class="internalDFN">preliminary CORS check</a> should be made available to web pages by a user agent. A user
           agent may provide a way for users to white-list non-CORS enabled Local-networked Services but implementation
           of such a feature is left to the discretion of the implementer.
      </p>
      <p>
        If a service connectivity request is successful then the Web page is provided with a promise-based success
        callback with the all necessary information to communicate with the authorized Local-networked Service. If the
        request fails then the Web page will receive a promise-based error callback containing an error string
        describing the cause of Local-networked Service connectivity failure.
      </p>
      <p>
        Once connected to a Local-networked Service the Web page can send requests and receive responses to the
        Local-networked Service via the messaging format and appropriate channel inferred from the service type
        authorized via the provided <abbr title="Application Programming Interface">API</abbr>. The Web page, once
        connected, can also receive service-pushed events, in the messaging format supported by the Local-networked
        Device, if such event subscription functionality is provided by the connected Local-networked Service.
      </p>
      <p>
        Services available within the local network can connect and disconnect at different times during the execution
        of a web page. The user agent can inform a web page when the state of networked services matching any of the
        requested valid service types change. Web pages can use this information to enable in-page experiences for
        communicating the state of networked services with the ability to change the particular service or set of
        services the page is connected to (by re-invoking the <a href=
        "#dom-navigator-getnetworkservices"><code>getNetworkServices()</code></a> method defined herein).
      </p>
      <div class="example">
        <p>
          Example of requesting a <abbr title="Domain Name System">DNS</abbr>-<abbr title="Service Discovery">SD</abbr>
          advertised service:
        </p>
        <hr>
        <pre class="highlight prettyprint">
<span class="kwd">function</span><span class="pln"> showServices</span><span class="pun">(</span><span class=
"pln"> services </span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
  </span><span class="com">// Show a list of all the services provided to the web page</span><span class="pln">
  </span><span class="kwd">for</span><span class="pun">(</span><span class="kwd">var</span><span class=
"pln"> i </span><span class="pun">=</span><span class="pln"> </span><span class="lit">0</span><span class=
"pun">,</span><span class="pln"> l </span><span class="pun">=</span><span class="pln"> services</span><span class=
"pun">.</span><span class="pln">length</span><span class="pun">;</span><span class="pln"> i </span><span class=
"pun">&lt;</span><span class="pln"> l</span><span class="pun">;</span><span class="pln"> i</span><span class=
"pun">++)</span><span class="pln"> console</span><span class="pun">.</span><span class="pln">log</span><span class=
"pun">(</span><span class="pln"> services</span><span class="pun">[</span><span class="pln">i</span><span class=
"pun">].</span><span class="pln">name </span><span class="pun">);</span><span class="pln">
</span><span class="pun">}</span><span class="pln">

navigator</span><span class="pun">.</span><span class="pln">getNetworkServices</span><span class=
"pun">(</span><span class="str">'zeroconf:_boxee-jsonrpc._tcp'</span><span class="pun">).</span><span class=
"kwd">then</span><span class="pun">(</span><span class="pln">showServices</span><span class="pun">);</span>
</pre>
      </div>
      <div class="example">
        <p>
          Example of requesting a UPnP advertised service, also handling error conditions:
        </p>
        <hr>
        <pre class="highlight prettyprint">
<span class="kwd">function</span><span class="pln"> showServices</span><span class="pun">(</span><span class=
"pln"> services </span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
  </span><span class="com">// Show a list of all the services provided to the web page</span><span class="pln">
  </span><span class="kwd">for</span><span class="pun">(</span><span class="kwd">var</span><span class=
"pln"> i </span><span class="pun">=</span><span class="pln"> </span><span class="lit">0</span><span class=
"pun">,</span><span class="pln"> l </span><span class="pun">=</span><span class="pln"> services</span><span class=
"pun">.</span><span class="pln">length</span><span class="pun">;</span><span class="pln"> i </span><span class=
"pun">&lt;</span><span class="pln"> l</span><span class="pun">;</span><span class="pln"> i</span><span class=
"pun">++)</span><span class="pln"> console</span><span class="pun">.</span><span class="pln">log</span><span class=
"pun">(</span><span class="pln"> services</span><span class="pun">[</span><span class="pln">i</span><span class=
"pun">].</span><span class="pln">name </span><span class="pun">);</span><span class="pln">
</span><span class="pun">}</span><span class="pln">

</span><span class="kwd">function</span><span class="pln"> error</span><span class="pun">(</span><span class=
"pln"> e </span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
  console</span><span class="pun">.</span><span class="pln">log</span><span class="pun">(</span><span class=
"pln"> </span><span class="str">"Error occurred: "</span><span class="pln"> </span><span class=
"pun">+</span><span class="pln"> e</span><span class="pun">.</span><span class="pln">name </span><span class=
"pun">);</span><span class="pln">
</span><span class="pun">}</span><span class="pln">

navigator</span><span class="pun">.</span><span class="pln">getNetworkServices</span><span class=
"pun">(</span><span class="str">'upnp:urn:schemas-upnp-org:service:ContentDirectory:1'</span><span class=
"pun">).</span><span class="kwd">then</span><span class="pun">(</span><span class="pln">showServices</span><span class=
"pun">,</span><span class="pln"> error</span><span class="pun">);</span>
</pre>
      </div>
      <div class="example">
        <p>
          Example of requesting either a <abbr title="Domain Name System">DNS</abbr>-<abbr title=
          "Service Discovery">SD</abbr> or UPnP advertised service:
        </p>
        <hr>
        <pre class="highlight prettyprint">
<span class="kwd">function</span><span class="pln"> showServices</span><span class="pun">(</span><span class=
"pln"> services </span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
  </span><span class=
"com">// Show a list of all the services provided to the web page (+ service type)</span><span class="pln">
  </span><span class="kwd">for</span><span class="pun">(</span><span class="kwd">var</span><span class=
"pln"> i </span><span class="pun">=</span><span class="pln"> </span><span class="lit">0</span><span class=
"pun">,</span><span class="pln"> l </span><span class="pun">=</span><span class="pln"> services</span><span class=
"pun">.</span><span class="pln">length</span><span class="pun">;</span><span class="pln"> i </span><span class=
"pun">&lt;</span><span class="pln"> l</span><span class="pun">;</span><span class="pln"> i</span><span class=
"pun">++)</span><span class="pln">
     console</span><span class="pun">.</span><span class="pln">log</span><span class="pun">(</span><span class=
"pln"> services</span><span class="pun">[</span><span class="pln">i</span><span class="pun">].</span><span class=
"pln">name </span><span class="pun">+</span><span class="pln"> </span><span class="str">'('</span><span class=
"pln"> </span><span class="pun">+</span><span class="pln"> services</span><span class="pun">[</span><span class=
"pln">i</span><span class="pun">].</span><span class="pln">type </span><span class="pun">+</span><span class=
"pln"> </span><span class="str">')'</span><span class="pln"> </span><span class="pun">);</span><span class="pln">
</span><span class="pun">}</span><span class="pln">

navigator</span><span class="pun">.</span><span class="pln">getNetworkServices</span><span class=
"pun">([</span><span class="pln">
  </span><span class="str">'zeroconf:_boxee-jsonrpc._tcp'</span><span class="pun">,</span><span class="pln">
  </span><span class="str">'upnp:urn:schemas-upnp-org:service:ContentDirectory:1'</span><span class="pln">
</span><span class="pun">]).</span><span class="kwd">then</span><span class="pun">(</span><span class=
"pln">showServices</span><span class="pun">);</span>
</pre>
      </div>
      <p>
        For more detailed examples, including examples of communicating with obtained networked services, see the
        <a href="#examples">Examples</a> section.
      </p>
    </section>
    <section id="conformance"
             typeof="bibo:Chapter"
             resource="#ref"
             rel="bibo:Chapter">
      <h2 aria-level="1"
          role="heading"
          id="h2_conformance">
        <span class="secno">2.</span> Conformance
      </h2>
      <p>
        As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this
        specification are non-normative. Everything else in this specification is normative.
      </p>
      <p>
        The key words <em class="rfc2119"
           title="MUST">MUST</em>, <em class="rfc2119"
           title="MUST NOT">MUST NOT</em>, <em class="rfc2119"
           title="REQUIRED">REQUIRED</em>, <em class="rfc2119"
           title="SHOULD">SHOULD</em>, <em class="rfc2119"
           title="SHOULD NOT">SHOULD NOT</em>, <em class="rfc2119"
           title="RECOMMENDED">RECOMMENDED</em>, <em class="rfc2119"
           title="MAY">MAY</em>, and <em class="rfc2119"
           title="OPTIONAL">OPTIONAL</em> in this specification are to be interpreted as described in [<cite><a class=
           "bibref"
           href="#bib-RFC2119">RFC2119</a></cite>].
      </p>
      <p>
        Requirements phrased in the imperative as part of algorithms (such as "strip any leading space characters" or
        "return false and abort these steps") are to be interpreted with the meaning of the key word ("must", "should",
        "may", etc) used in introducing the algorithm.
      </p>
      <p>
        Some conformance requirements are phrased as requirements on attributes, methods or objects. Such requirements
        are to be interpreted as requirements on user agents.
      </p>
      <p>
        Conformance requirements phrased as algorithms or specific steps <em class="rfc2119"
           title="MAY">MAY</em> be implemented in any manner, so long as the end result is equivalent. (In particular,
           the algorithms defined in this specification are intended to be easy to follow, and not intended to be
           performant.)
      </p>
      <p>
        The only conformance class defined by this specification is a <dfn id="dfn-user-agent">user agent</dfn>.
      </p>
      <p>
        User agents <em class="rfc2119"
           title="MAY">MAY</em> impose implementation-specific limits on otherwise unconstrained inputs, e.g. to
           prevent denial of service attacks, to guard against running out of memory, or to work around
           platform-specific limitations.
      </p>
      <p>
        When support for a feature is disabled (e.g. as an emergency measure to mitigate a security problem, or to aid
        in development, or for performance reasons), user agents <em class="rfc2119"
           title="MUST">MUST</em> act as if they had no support for the feature whatsoever, and as if the feature was
           not mentioned in this specification. For example, if a particular feature is accessed via an attribute in a
           Web IDL interface, the attribute itself would be omitted from the objects that implement that interface -
           leaving the attribute on the object but making it return null or throw an exception is insufficient.
      </p>
      <section id="dependencies">
        <h3 aria-level="2"
            role="heading"
            id="h3_dependencies">
          <span class="secno">2.1</span> Dependencies
        </h3>This specification relies on several other underlying specifications.
        <dl>
          <dt>
            HTML
          </dt>
          <dd>
            Many fundamental concepts from HTML are used by this specification. [<cite><a class="bibref"
               href="#bib-HTML5">HTML5</a></cite>]
          </dd>
          <dt>
            WebIDL
          </dt>
          <dd>
            The IDL blocks in this specification use the semantics of the WebIDL specification. [<cite><a class=
            "bibref"
               href="#bib-WEBIDL">WEBIDL</a></cite>]
          </dd>
        </dl>
      </section>
    </section>
    <section id="terminology">
      <h2 aria-level="1"
          role="heading"
          id="h2_terminology">
        <span class="secno">3.</span> Terminology
      </h2>
      <p>
        The construction "a <code>Foo</code> object", where <code>Foo</code> is actually an interface, is sometimes
        used instead of the more accurate "an object implementing the interface <code>Foo</code>".
      </p>
      <p>
        The term DOM is used to refer to the <abbr title="Application Programming Interface">API</abbr> set made
        available to scripts in Web applications, and does not necessarily imply the existence of an actual
        <code>Document</code> object or of any other <code>Node</code> objects as defined in the DOM Core
        specifications. [<cite><a class="bibref"
           href="#bib-DOM4">DOM4</a></cite>]
      </p>
      <p>
        An IDL attribute is said to be <em>getting</em> when its value is being retrieved (e.g. by author script), and
        is said to be <em>setting</em> when a new value is assigned to it.
      </p>
      <p>
        A <dfn id="dfn-valid-service-type">valid service type</dfn> is any of the following:
      </p>
      <ul>
        <li>a string that begins with <code>upnp:</code> or <code>zeroconf:</code> followed by one or more characters
        in the ranges U+0021, U+0023 to U+0027, U+002A to U+002B, U+002D to U+002E, U+0030 to U+0039, U+0041 to U+005A,
        U+005E to U+007E.
        </li>
        <li>a string that begins with <code>dial:</code> followed by an integer version.
        </li>
      </ul>
      <p>
        A <a href="#dfn-valid-service-type"
           class="internalDFN">valid service type</a> provided in the <code>type</code> attribute of the <a href=
           "#dom-navigator-getnetworkservices"><code>getNetworkServices()</code></a> method will be matched against the
           services currently contained in the <a href="#dfn-list-of-available-service-records"
           class="internalDFN">list of available service records</a> according to the algorithms defined in this
           specification.
      </p>
      <p>
        A <dfn id="dfn-user-agent-generated-callback-url">user-agent generated callback url</dfn> is a Local-network
        accessible URL endpoint that a <a href="#dfn-user-agent"
           class="internalDFN">user agent</a> generates and maintains for receiving <abbr title=
           "Hypertext Transfer Protocol">HTTP</abbr> NOTIFY requests from UPnP Event sources. It is only required when
           the user agent implements UPnP Service Discovery as defined in this specification.
      </p>
      <p>
        In this specification we use the following terms to describe the processes required for Local-networked
        Services management:
      </p>
      <ul>
        <li>A <dfn id="dfn-new-service">new service</dfn> is a Local-networked Service that has not previously been
        discovered or registered in the <a href="#dfn-list-of-available-service-records"
              class="internalDFN">list of available service records</a>.
        </li>
        <li>An <dfn id="dfn-existing-service">existing service</dfn> is a Local-networked Service that has previously
        been discovered and is registered in the <a href="#dfn-list-of-available-service-records"
              class="internalDFN">list of available service records</a>.
        </li>
        <li>A <dfn id="dfn-current-service">current service</dfn> is a Local-networked Service, represented by a
        <a href="#networkservice"><code>NetworkService</code></a> object, that is currently being shared with a web
        page via a <a href="#networkservices"><code>NetworkServices</code></a> object registered in the <a href=
        "#dfn-list-of-active-service-managers"
              class="internalDFN">list of active service managers</a>.
        </li>
      </ul>
      <p>
        A <dfn id="dfn-network-services-whitelist">network services whitelist</dfn> is a list of zero or more <a href=
        "#dfn-valid-service-type"
           class="internalDFN">valid service type</a> tokens that, when matched to a service type discovered in the
           local network, enables that service to be shared with a web page even if that Local-networked Service does
           not itself allow Cross-Origin Resource Sharing [<cite><a class="bibref"
           href="#bib-CORS">CORS</a></cite>]. A <a href="#dfn-user-agent"
           class="internalDFN">user agent</a> <em class="rfc2119"
           title="MUST">MUST</em> simulate CORS support for all service interaction in this case. Implementation of
           this feature is at implementer's discretion. When a <a href="#dfn-user-agent"
           class="internalDFN">user agent</a> does not implement a <a href="#dfn-network-services-whitelist"
           class="internalDFN">network services whitelist</a> then it is to treat this as always being an empty list.
      </p>
    </section>
    <section id="security-and-privacy-considerations">
      <h2 aria-level="1"
          role="heading"
          id="h2_security-and-privacy-considerations">
        <span class="secno">4.</span> Security and privacy considerations
      </h2>
      <p>
        The <abbr title="Application Programming Interface">API</abbr> defined in this specification can be used to
        find and connect to devices and services within a user's current network. This discloses information related to
        a user's network: devices available on their network and the publicly-accessible services ("networked
        services") currently running and available on those devices. The distribution of this information could
        potentially compromise the user's privacy. A conforming implementation of this specification <em class=
        "rfc2119"
           title="MUST">MUST</em> provide a mechanism that protects the user's privacy. This mechanism <em class=
           "rfc2119"
           title="MUST">MUST</em> ensure that no networked service information is retrievable without the user's
           express permission.
      </p>
      <section id="security-considerations-for-api-implementations">
        <h3 aria-level="2"
            role="heading"
            id="h3_security-considerations-for-api-implementations">
          <span class="secno">4.1</span> Security considerations for <abbr title=
          "Application Programming Interface">API</abbr> implementations
        </h3>
        <p>
          A <a href="#dfn-user-agent"
             class="internalDFN">user agent</a> <em class="rfc2119"
             title="SHOULD">SHOULD</em> only allow web pages to connect with Local-networked Services that have passed
             a <a href="#dfn-preliminary-cors-check"
             class="internalDFN">preliminary CORS check</a> indicating they support Cross-Origin Resource Sharing
             [<cite><a class="bibref"
             href="#bib-CORS">CORS</a></cite>]. In this way, a <a href="#dfn-user-agent"
             class="internalDFN">user agent</a> <em class="rfc2119"
             title="SHOULD NOT">SHOULD NOT</em> allow web pages to access other arbitrary networked services on the
             current local network.
        </p>
        <p>
          A <a href="#dfn-user-agent"
             class="internalDFN">user agent</a> <em class="rfc2119"
             title="MAY">MAY</em> provide a way for users to enable access to non-CORS enabled Local-networked Services
             from web pages (i.e. operate a <a href="#dfn-network-services-whitelist"
             class="internalDFN">network services whitelist</a>). Implementation of such a <a href=
             "#dfn-network-services-whitelist"
             class="internalDFN">network services whitelist</a>, if any, is left to an implementer's discretion. Such a
             whitelist may be configurable by each user at runtime or may be managed by the implementation itself on
             behalf of its users. In the case that a <a href="#dfn-user-agent"
             class="internalDFN">user agent</a> provides a <a href="#dfn-network-services-whitelist"
             class="internalDFN">network services whitelist</a>, it <em class="rfc2119"
             title="MUST">MUST</em> act as if all URLs for the Local-networked Service corresponding to any previously
             whitelisted service type had Cross-Origin Resource Sharing [<cite><a class="bibref"
             href="#bib-CORS">CORS</a></cite>] enabled indefinitely.
        </p>
      </section>
      <section id="privacy-considerations-for-api-implementations">
        <h3 aria-level="2"
            role="heading"
            id="h3_privacy-considerations-for-api-implementations">
          <span class="secno">4.2</span> Privacy considerations for <abbr title=
          "Application Programming Interface">API</abbr> implementations
        </h3>
        <p>
          A <a href="#dfn-user-agent"
             class="internalDFN">user agent</a> <em class="rfc2119"
             title="MUST NOT">MUST NOT</em> provide networked service information to web sites without the express
             permission of the user. A user agent <em class="rfc2119"
             title="MUST">MUST</em> acquire permission through a user interface, unless they have prearranged trust
             relationships with users, as described below. The user interface <em class="rfc2119"
             title="MUST">MUST</em> include the document base URL. Those permissions that are acquired through the user
             interface and that are preserved beyond the current browsing session (i.e. beyond the time when the
             browsing context is navigated to another URL) <em class="rfc2119"
             title="MUST">MUST</em> be revocable and a user agent <em class="rfc2119"
             title="MUST">MUST</em> respect revoked permissions.
        </p>
        <p>
          Obtaining the user's express permission to access one <abbr title=
          "Application Programming Interface">API</abbr> method does not imply the user has granted permission for the
          same web site to access any other methods that may be provided by this <abbr title=
          "Application Programming Interface">API</abbr>, or to access the same method with a different set of
          arguments, as part of the same permission context. If a user has expressed permission for an implementation
          to, e.g. find a set of existing networked services, the implementation <em class="rfc2119"
             title="MUST">MUST</em> seek the user's express permission if and when any subsequent functions are called
             on this <abbr title="Application Programming Interface">API</abbr>.
        </p>
        <p>
          A user agent <em class="rfc2119"
             title="MAY">MAY</em> have prearranged trust relationships that do not require such user interfaces. For
             example, while a web browser will present a user interface when a web site performs a networked service
             lookup, a different runtime may have a prearranged, delegated security relationship with the user and, as
             such, a suitable alternative security and privacy mechanism with which to authorise the retrieval of
             networked service information.
        </p>
      </section>
      <section class="informative"
               id="additional-api-implementation-considerations">
        <h3 aria-level="2"
            role="heading"
            id="h3_additional-api-implementation-considerations">
          <span class="secno">4.3</span> Additional <abbr title="Application Programming Interface">API</abbr>
          implementation considerations
        </h3>
        <p>
          <em>This section is non-normative.</em>
        </p>
        <p>
          Further to the requirements listed in the previous section, implementers of the Network Service Discovery
          <abbr title="Application Programming Interface">API</abbr> are also advised to consider the following aspects
          that can negatively affect the privacy of their users: in certain cases, users can inadvertently grant
          permission to the user agent to disclose networked services to Web sites. In other cases, the content hosted
          at a certain URL changes in such a way that previously granted networked service permissions no longer apply
          as far as the user is concerned. Or the users might simply change their minds.
        </p>
        <p>
          Predicting or preventing these situations is inherently difficult. Mitigation and in-depth defensive measures
          are an implementation responsibility and not prescribed by this specification. However, in designing these
          measures, implementers are advised to enable user awareness of networked service sharing, and to provide easy
          access to interfaces that enable revocation of permissions that web applications have for accessing networked
          services via this <abbr title="Application Programming Interface">API</abbr>.
        </p>
      </section>
    </section>
    <section id="requesting-networked-services">
      <h2 aria-level="1"
          role="heading"
          id="h2_requesting-networked-services">
        <span class="secno">5.</span> Requesting networked services
      </h2>
      <pre class="widl">
[Supplemental, NoInterfaceObject]
interface <dfn id="navigatornetworkservice">NavigatorNetworkService</dfn> {
  <a class="externalDFN"
     href="http://dom.spec.whatwg.org/#promise">Promise</a> <a href=
     "#dom-navigator-getnetworkservices">getNetworkServices</a>( in any type );
};

<a class="externalDFN"
     href=
     "http://www.whatwg.org/specs/web-apps/current-work/complete/timers.html#navigator">Navigator</a> implements <a href=
     "#navigatornetworkservice">NavigatorNetworkService</a>;
</pre>
      <section id="methods">
        <h3 aria-level="2"
            role="heading"
            id="h3_methods">
          <span class="secno">5.1</span> Methods
        </h3>
        <dl class="domintro">
          <dt>
            <var title="">promise</var> = <var title="">window</var> . <code title="dom-navigator"><a href=
            "http://www.whatwg.org/specs/web-apps/current-work/complete/timers.html#navigator">navigator</a></code> .
            <code title="dom-navigator-getNetworkServices"><a href=
            "#dom-navigator-getnetworkservices">getNetworkServices</a></code> ( <var title="">type</var> )
          </dt>
          <dd>
            <p>
              Immediately returns a new <a href="http://dom.spec.whatwg.org/#promise"
                 class="externalDFN">Promise</a> object and then the user is prompted to select discovered network
                 services that have advertised support for the requested service type(s).
            </p>
            <p>
              The <var title="">type</var> argument contains one or more <a href="#dfn-valid-service-type"
                 class="internalDFN">valid service type</a> tokens that the web page would like to interact with.
            </p>
            <p>
              If the user accepts, the <var title="">promise</var> object is <a class="externalDFN"
                 href="http://dom.spec.whatwg.org/#concept-resolver-resolve">resolved</a>, with a <a href=
                 "#networkservices"><code>NetworkServices</code></a> object as its argument.
            </p>
            <p>
              If the user declines, or an error occurs, the <var title="">promise</var> object is <a class=
              "externalDFN"
                 href="http://dom.spec.whatwg.org/#concept-resolver-reject">rejected</a>.
            </p>
          </dd>
        </dl>
        <div>
          <p>
            When the <dfn id="dom-navigator-getnetworkservices"
               title="dom-navigator-getnetworkservices"><code>getNetworkServices(type)</code></dfn> method is called,
               the <a href="#dfn-user-agent"
               class="internalDFN">user agent</a> <em class="rfc2119"
               title="MUST">MUST</em> run the following steps:
          </p>
          <ol class="rule">
            <li>Let <var>Network Service Promise</var> be a new <a href="http://dom.spec.whatwg.org/#promise"
                  class="externalDFN"><code>Promise</code></a> object.
            </li>
            <li>Let <var>Network Service Promise's Resolver</var> be the default <a href=
            "http://dom.spec.whatwg.org/#concept-resolver"
                  class="externalDFN">resolver</a> of <var>Network Service Promise</var>.
            </li>
            <li>Return <var>Network Service Promise</var>, and run the remaining steps asynchronously.
            </li>
            <li>Let <var>requested control types</var> be initially set to an empty array.
            </li>
            <li>If <var>type</var> is an array consisting of one or more <a href="#dfn-valid-service-type"
                  class="internalDFN">valid service type</a> tokens, then let <var>requested control types</var> be the
                  value of <var>type</var>, removing any non-<a href="#dfn-valid-service-type"
                  class="internalDFN">valid service type</a> tokens from the resulting array.
            </li>
            <li>If <var>type</var> is a string consisting of one <a href="#dfn-valid-service-type"
                  class="internalDFN">valid service type</a> token, then let <var>requested control types</var> be an
                  array containing one item with a value of <var>type</var>.
            </li>
            <li>If <var>requested control types</var> is an array that contains at least one or more <a title=
            "valid service type"
                  href="#dfn-valid-service-type"
                  class="internalDFN">valid service type</a> tokens then continue to the step labeled <em>process</em>
                  below. Otherwise, reject <var>Network Service Promise</var> by running the <a href=
                  "http://dom.spec.whatwg.org/#concept-resolver-reject"
                  class="externalDFN">resolver reject algorithm</a> against the <var>Network Service Promise's
                  Resolver</var>, passing in a newly constructed <a href="http://dom.spec.whatwg.org/#domerror"
                  class="externalDFN"><code>DOMError</code></a> object whose <code>name</code> attribute has the string
                  value "UnknownTypePrefixError" (<a href=
                  "#dom-domerror-extensions-unknown_type_prefix"><code>UNKNOWN_TYPE_PREFIX_ERR</code></a>) and whose
                  <code>message</code> attribute has a helpful implementation-dependent message that explains this
                  error, abort any remaining steps and return.
            </li>
            <li>
              <em>Process</em>: Let <var>services found</var> be an empty array.
            </li>
            <li>For each <var>available service</var> in the <a href="#dfn-list-of-available-service-records"
                  class="internalDFN">list of available service records</a> run the following steps:
              <ol class="rule">
                <li>For each <var>requested control type</var> in <var>requested control types</var>: If <var>available
                service</var>'s <code>type</code> attribute equals the <var>requested control type</var> then let <var>
                  matched service</var> equal the value of <var>available service</var>. Otherwise, abort the remaining
                  sub-steps and continue above at the next <var>available service</var>.
                </li>
                <li>If <var>matched service</var> is not empty then run the following steps:
                  <ol class="rule">
                    <li>Let <var>CORS check result</var> be the result of running the <a href=
                    "#dfn-preliminary-cors-check"
                          class="internalDFN">preliminary CORS check</a> algorithm, passing in <var>matched
                          services</var>'s <code>url</code> attribute as the <var>control endpoint URL</var> argument
                          and the <a href=
                          "http://www.whatwg.org/specs/web-apps/current-work/complete/browsers.html#entry-script"
                          class="externalDFN">entry script</a>'s <a href=
                          "http://www.whatwg.org/specs/web-apps/current-work/complete/origin-0.html#origin"
                          class="externalDFN">origin</a> as the <var>request origin</var> argument.
                    </li>
                    <li>If <var>CORS check result</var> is not <code>pass</code> and <var>matched service</var>'s
                    <code>type</code> attribute is also not present in the <a href="#dfn-network-services-whitelist"
                          class="internalDFN">network services whitelist</a> then abort the remaining sub-steps and
                          continue above at the next <var>available service</var>.
                    </li>
                    <li>Let <var>new service object</var> be a new <a href=
                    "#networkservice"><code>NetworkService</code></a> object, mapping the parameters of <var>matched
                    service</var> to this new object where possible.
                    </li>
                    <li>Append <var>new service object</var> to the <var>services found</var> array.
                    </li>
                  </ol>
                </li>
              </ol>
            </li>
            <li>Optionally, e.g. based on a previously-established user preference, for security reasons, or due to
            platform limitations, the <a href="#dfn-user-agent"
                  class="internalDFN">user agent</a> <em class="rfc2119"
                  title="MAY">MAY</em> reject <var>Network Service Promise</var> by running the <a href=
                  "http://dom.spec.whatwg.org/#concept-resolver-reject"
                  class="externalDFN">resolver reject algorithm</a> against the <var>Network Service Promise's
                  Resolver</var>, passing in a newly constructed <a href="http://dom.spec.whatwg.org/#domerror"
                  class="externalDFN"><code>DOMError</code></a> object whose <code>name</code> attribute has the string
                  value "PermissionDeniedError" (<a href=
                  "#dom-domerror-extensions-permission_denied"><code>PERMISSION_DENIED_ERR</code></a>) and whose
                  <code>message</code> attribute has a helpful implementation-dependent message that explains this
                  error, abort any remaining steps and return.
            </li>
            <li>The user agent <em class="rfc2119"
                  title="MUST NOT">MUST NOT</em> provide the entry script's origin with a <a href=
                  "#networkservices"><code>NetworkServices</code></a> object without prior permission given by the
                  user.
              <p>
                If <var>services found</var> is not an empty array then the <a href="#dfn-user-agent"
                   class="internalDFN">user agent</a> <em class="rfc2119"
                   title="MAY">MAY</em> choose to prompt the user in a user-agent-specific manner for permission to
                   provide the <a href=
                   "http://www.whatwg.org/specs/web-apps/current-work/complete/browsers.html#entry-script"
                   class="externalDFN">entry script</a>'s <a href=
                   "http://www.whatwg.org/specs/web-apps/current-work/complete/origin-0.html#origin"
                   class="externalDFN">origin</a> with a <a href="#networkservices"><code>NetworkServices</code></a>
                   object representing the <a href="#dfn-user-authorized"
                   class="internalDFN">user-authorized</a> subset of <var>services found</var>.
              </p>
              <p>
                Alternatively, the user agent <em class="rfc2119"
                   title="MAY">MAY</em> wish to skip this user opt-in step and choose to fulfill <var>Network Service
                   Promise</var> immediately based on a previously-established user preference, for security reasons,
                   or due to platform limitations. In such an implementation, if <var>Network Service Promise</var> is
                   to be fulfilled as a result of a previously-established user preference then the <a href=
                   "#dfn-user-agent"
                   class="internalDFN">user agent</a> <em class="rfc2119"
                   title="MUST">MUST</em> continue at the next step of this algorithm.
              </p>
              <p>
                If permission has been granted by the user to access one or more networked services then the <a href=
                "#dfn-user-agent"
                   class="internalDFN">user agent</a> <em class="rfc2119"
                   title="SHOULD">SHOULD</em> include an "ongoing local-network communication" indicator.
              </p>
              <p>
                If permission has been denied by the user, <a href="#dfn-user-agent"
                   class="internalDFN">user agent</a> or platform, then the <a href="#dfn-user-agent"
                   class="internalDFN">user agent</a> <em class="rfc2119"
                   title="MUST">MUST</em> reject <var>Network Service Promise</var> by running the <a href=
                   "http://dom.spec.whatwg.org/#concept-resolver-reject"
                   class="externalDFN">resolver reject algorithm</a> against the <var>Network Service Promise's
                   Resolver</var>, passing in a newly constructed <a href="http://dom.spec.whatwg.org/#domerror"
                   class="externalDFN"><code>DOMError</code></a> object whose <code>name</code> attribute has the
                   string value "PermissionDeniedError" (<a href=
                   "#dom-domerror-extensions-permission_denied"><code>PERMISSION_DENIED_ERR</code></a>) and whose
                   <code>message</code> attribute has a helpful implementation-dependent message that explains this
                   error, abort any remaining steps and return.
              </p>
              <p>
                If the user never responds or no previously-established user preference has been met, this algorithm
                stalls on this step.
              </p>
            </li>
            <li>Let <var>services</var> be an empty array.
            </li>
            <li>If <var>services found</var> is not an empty array then set <var>services</var> to be an array of one
            or more <a href="#networkservice"><code>NetworkService</code></a> objects for which the user granted
            permission above - known as the current objects <dfn id="dfn-user-authorized">user-authorized</dfn>
            services.
            </li>
            <li>For each Object <var>service</var> in <var>services</var>, if any, run the following sub-steps:
              <ol class="rule">
                <li>If <var>service</var>'s <code>type</code> parameter begins with the DOMString "<code>upnp:</code>"
                and the <var>service</var>'s <code>eventsUrl</code> parameter is not empty then <a href=
                "#dfn-setup-a-upnp-events-subscription"
                      class="internalDFN">setup a UPnP Events Subscription</a> for <var>service</var>.
                </li>
              </ol>
            </li>
            <li>Let <var>services manager</var> be a new <a href="#networkservices"><code>NetworkServices</code></a>
            object.
            </li>
            <li>Store <var>requested control types</var> against <var>services manager</var> as an internal variable.
            </li>
            <li>Set <var>services manager</var>'s <a href=
            "#dom-networkservices-servicesavailable"><code>servicesAvailable</code></a> attribute to the number of
            items currently found in the <a href="#dfn-list-of-available-service-records"
                  class="internalDFN">list of available service records</a> whose <code>type</code> property matches
                  any of the tokens requested in <var>requested control types</var>.
            </li>
            <li>Add <var>services</var>, if any, to the <var>services manager</var> object as its collection of
              <a href="#dfn-indexed-properties"
                  class="internalDFN">indexed properties</a>. If <var>services</var> is an empty array then the
                  <var>services manager</var> does not have any <var>indexed properties</var>.
            </li>
            <li>Set <var>services manager</var>'s <a href="#dom-networkservices-length"><code>length</code></a>
            attribute to the number of items in <var>services</var>.
            </li>
            <li>Add <var>services manager</var> to the <a href="#dfn-list-of-active-service-managers"
                  class="internalDFN">list of active service managers</a>.
            </li>
            <li>The <a href="#dfn-user-agent"
                  class="internalDFN">user agent</a> <em class="rfc2119"
                  title="MUST">MUST</em> fulfill <var>Network Service Promise</var> by running the <a href=
                  "http://dom.spec.whatwg.org/#concept-resolver-fulfill"
                  class="externalDFN">resolver fulfill algorithm</a> against the <var>Network Service Promise's
                  Resolver</var>, passing in <var>services manager</var> as its argument.
            </li>
          </ol>
          <p>
            The <a href="http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#task-source"
               class="externalDFN">task source</a> for these <a href=
               "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#concept-task"
               class="externalDFN">tasks</a> is the <a href=
               "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#user-interaction-task-source"
               class="externalDFN">user interaction task source</a>.
          </p>
          <p>
            The <dfn id="dfn-preliminary-cors-check">preliminary CORS check</dfn> algorithm determines whether a
            Local-networked Service supports Cross-Origin Resource Sharing [<cite><a class="bibref"
               href="#bib-CORS">CORS</a></cite>] as part of a call to the <a href=
               "#dom-navigator-getnetworkservices"><code>getNetworkServices()</code></a> method, prior to that service
               being proposed for sharing to users and prior to active sharing with web pages. This algorithm takes two
               arguments, <var>control endpoint URL</var> and <var>request origin</var>, and consists of running the
               following steps:
          </p>
          <ol class="rule">
            <li>Let <var>CORS available check</var> be the result of applying the <a href=
            "http://www.w3.org/TR/cors/#make-a-request-steps"
                  class="externalDFN">make a request steps</a> [<cite><a class="bibref"
                 href="#bib-CORS">CORS</a></cite>], setting the <a href="http://www.w3.org/TR/cors/#request-method"
                  class="externalDFN">request method</a> to <code>OPTIONS</code>, the <a href=
                  "http://www.w3.org/TR/cors/#request-url"
                  class="externalDFN">request URL</a> to <var>control endpoint URL</var>, the <a href=
                  "http://www.w3.org/TR/cors/#source-origin"
                  class="externalDFN">source origin</a> to <var>request origin</var>, setting the <a href=
                  "http://www.w3.org/TR/cors/#omit-credentials-flag"
                  class="externalDFN">omit credentials flag</a> to <code>true</code> and including an <a href=
                  "http://www.w3.org/TR/cors/#http-access-control-request-method"
                  class="externalDFN"><code>Access-Control-Request-Method</code></a> header with a value of
                  <code>GET</code>.
            </li>
            <li>If <var>CORS available check</var> is cancelled by the user, or it results in a network error, or its
            response does not have an <abbr title="Hypertext Transfer Protocol">HTTP</abbr> status code of
            <code>200</code> then abort any remaining steps and return <code>fail</code>.
            </li>
            <li>Return the result of running the <a href="http://www.w3.org/TR/cors/#resource-sharing-check"
                  class="externalDFN">resource sharing check</a> [<cite><a class="bibref"
                 href="#bib-CORS">CORS</a></cite>] against the successful <abbr title=
                 "Hypertext Transfer Protocol">HTTP</abbr> response of the <var>CORS available check</var>.
              <div class="note">
                <div class="note-title"
                     aria-level="3"
                     role="heading"
                     id="h_note_1">
                  <span>Note</span>
                </div>
                <p class="">
                  This returned result will always be either <code>pass</code> or <code>fail</code>.
                </p>
              </div>
            </li>
          </ol>
          <p>
            There is no implied persistence to networked service sharing provided to a web page. It <em class="rfc2119"
               title="MUST NOT">MUST NOT</em> be possible to access a networked service previously granted to a web
               page without user authorization in all of the following cases:
          </p>
          <ul>
            <li>If the current script is reloaded at any point in the same or different window.
            </li>
            <li>if the current script reinvokes the <a href=
            "#dom-navigator-getnetworkservices"><code>getNetworkServices()</code></a> method at any point in its
            execution.
            </li>
            <li>If the user navigates forward or back in their history to reload the current page.
            </li>
            <li>If a script is running in a different origin.
            </li>
          </ul>
        </div>
      </section>
      <section id="error-handling">
        <h3 aria-level="2"
            role="heading"
            id="h3_error-handling">
          <span class="secno">5.2</span> Error Handling
        </h3>
        <dl class="domintro">
          <dt>
            <var title="">error</var> . <code title="dom-NavigatorNetworkServiceError-name"><a href=
            "#dom-domerror-extensions-name">name</a></code>
          </dt>
          <dd>
            <p>
              Returns the current error's error name. At the current time, this will be "PermissionDeniedError" or
              "UnknownTypePrefixError", for which the corresponding error constants <a href=
              "#dom-domerror-extensions-permission_denied"><code>PERMISSION_DENIED_ERR</code></a> and <a href=
              "#dom-domerror-extensions-unknown_type_prefix"><code>UNKNOWN_TYPE_PREFIX_ERR</code></a> are defined.
            </p>
          </dd>
        </dl>
        <p>
          The <dfn id="dom-domerror-extensions-name"
             title="dom-domerror-extensions-name"><code>name</code></dfn> attribute of a <a href=
             "http://dom.spec.whatwg.org/#domerror"
             class="externalDFN"><code>DOMError</code></a> object returned from this <abbr title=
             "Application Programming Interface">API</abbr> <em class="ct"><em class="rfc2119"
              title="MUST">MUST</em></em> return the name for the error, which will be one of the following:
        </p>
        <dl>
          <dt>
            <dfn id="dom-domerror-extensions-permission_denied"
                title="dom-domerror-extensions-permission_denied"><code>PERMISSION_DENIED_ERR</code></dfn> (DOMString
                value "PermissionDeniedError")
          </dt>
          <dd>
            The user or user agent denied the page permission to access any services.
          </dd>
          <dt>
            <dfn id="dom-domerror-extensions-unknown_type_prefix"
                title="dom-domerror-extensions-unknown_type_prefix"><code>UNKNOWN_TYPE_PREFIX_ERR</code></dfn>
                (DOMString value "UnknownTypePrefixError")
          </dt>
          <dd>
            No <a href="#dfn-valid-service-type"
                class="internalDFN">valid service type</a> tokens were provided in the method invocation.
          </dd>
        </dl>
      </section>
    </section>
    <section id="obtaining-networked-services">
      <h2 aria-level="1"
          role="heading"
          id="h2_obtaining-networked-services">
        <span class="secno">6.</span> Obtaining networked services
      </h2>
      <p>
        The <a href="#networkservices"><code>NetworkServices</code></a> interface represents a collection of zero or
        more <a href="#dfn-indexed-properties"
           class="internalDFN">indexed properties</a> that are each a <a href="#dfn-user-authorized"
           class="internalDFN">user-authorized</a> <a href="#networkservice"><code>NetworkService</code></a> object.
      </p>
      <p>
        A <a href="#networkservices"><code>NetworkServices</code></a> object is the <a href=
        "http://dom.spec.whatwg.org/#concept-promise-result"
           class="externalDFN">promise result</a> from a call to <a href=
           "#dom-navigator-getnetworkservices"><code>getNetworkServices()</code></a>.
      </p>
      <pre class="widl">
[NoInterfaceObject]
interface <dfn id="networkservices">NetworkServices</dfn> {
  readonly attribute unsigned long    <a href="#dom-networkservices-length">length</a>;
  getter <a href="#networkservice">NetworkService</a> (unsigned long index);
  <a href="#networkservice">NetworkService</a>? <a href=
"#dom-networkservices-getservicebyid">getServiceById</a>(DOMString id);

  readonly attribute unsigned long    <a href="#dom-networkservices-servicesavailable">servicesAvailable</a>;

  // event handler attributes
           attribute <a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#eventhandler"
     class="externalDFN">EventHandler</a>     <a href="#dom-networkservices-onservicefound">onservicefound</a>;
           attribute <a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#eventhandler"
     class="externalDFN">EventHandler</a>     <a href="#dom-networkservices-onservicelost">onservicelost</a>;

};

<a href="#networkservices">NetworkServices</a> implements <a href=
"http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#interface-eventtarget"
     class="externalDFN">EventTarget</a>;
</pre>
      <section id="attributes">
        <h3 aria-level="2"
            role="heading"
            id="h3_attributes">
          <span class="secno">6.1</span> Attributes
        </h3>
        <dl class="domintro">
          <dt>
            <code title="dom-networkservices-length"><a href="#dom-networkservices-length">length</a></code>
          </dt>
          <dd>
            <p>
              Returns the current number of <a href="#dfn-indexed-properties"
                 class="internalDFN">indexed properties</a> in the current object's collection.
            </p>
          </dd>
          <dt>
            <code title="dom-networkservices-servicesavailable"><a href=
            "#dom-networkservices-servicesavailable">servicesAvailable</a></code>
          </dt>
          <dd>
            <p>
              Returns the current number of items matching one of the app-requested <a href="#dfn-valid-service-type"
                 class="internalDFN">valid service type</a> tokens in the <a href=
                 "#dfn-list-of-available-service-records"
                 class="internalDFN">list of available service records</a>.
            </p>
          </dd>
        </dl>
        <div>
          <p>
            The <dfn id="dom-networkservices-length"><code>length</code></dfn> attribute <em class="rfc2119"
               title="MUST">MUST</em> return the number of <a href="#networkservice"><code>NetworkService</code></a>
               objects represented by the collection.
          </p>
          <p>
            The <dfn id="dom-networkservices-servicesavailable"><code>servicesAvailable</code></dfn> attribute
            <em class="rfc2119"
               title="MUST">MUST</em> return the number of services in the <a href=
               "#dfn-list-of-available-service-records"
               class="internalDFN">list of available service records</a> whose <code>type</code> attribute matches any
               of the <a href="#dfn-valid-service-type"
               class="internalDFN">valid service type</a> tokens that were initially used to create the current <a href=
               "#networkservices"><code>NetworkServices</code></a> object.
          </p>
        </div>
      </section>
      <section id="methods-1">
        <h3 aria-level="2"
            role="heading"
            id="h3_methods-1">
          <span class="secno">6.2</span> Methods
        </h3>
        <dl class="domintro">
          <dt>
            <code title="networkservices-getter"><a href="#networkservices">services</a></code> [ <var title=
            "">index</var> ]
          </dt>
          <dd>
            <p>
              Returns the specified <a href="#networkservice"><code>NetworkService</code></a> object.
            </p>
          </dd>
          <dt>
            <code title="networkservices-getter"><a href="#networkservices">services</a></code> . <code title=
            "dom-networkservices-getservicebyid"><a href=
            "#dom-networkservices-getservicebyid">getServiceById</a></code> ( <var title="">id</var> )
          </dt>
          <dd>
            <p>
              Returns the <a href="#networkservice"><code>NetworkService</code></a> object with the given identifier,
              or null if no service has that identifier.
            </p>
          </dd>
        </dl>
        <p>
          A <a href="#networkservices"><code>NetworkServices</code></a> object represents the current collection of
          zero or more <a href="#networkservice"><code>NetworkService</code></a> objects - its <a href=
          "#dfn-indexed-properties"
             class="internalDFN">indexed properties</a>. The <a href="#dfn-indexed-properties"
             class="internalDFN">indexed properties</a> of a <a href=
             "#networkservices"><code>NetworkServices</code></a> object are <span>immutable</span> meaning that <a href=
             "#dfn-indexed-properties"
             class="internalDFN">indexed properties</a> cannot be added and <a href="#dfn-indexed-properties"
             class="internalDFN">indexed properties</a> cannot be removed for the lifetime of a <a href=
             "#networkservices"><code>NetworkServices</code></a> object.
        </p>
        <p>
          The <a href=
          "http://www.whatwg.org/specs/web-apps/current-work/multipage/infrastructure.html#supported-property-indices"
             class="externalDFN">supported property indices</a> of <a href=
             "#networkservices"><code>NetworkServices</code></a> objects at any instant are the numbers from zero to
             the number of the <a href="#networkservice"><code>NetworkService</code></a> objects in the collection
             minus one.
        </p>
        <div class="note">
          <div class="note-title"
               aria-level="3"
               role="heading"
               id="h_note_2">
            <span>Note</span>
          </div>
          <p class="">
            Each service in a <a href="#networkservices"><code>NetworkServices</code></a> object thus has an index; the
            first has the index 0, and each subsequent service is numbered one higher than the previous one.
          </p>
        </div>
        <p>
          To <a href=
          "http://www.whatwg.org/specs/web-apps/current-work/multipage/infrastructure.html#determine-the-value-of-an-indexed-property"
             class="externalDFN">determine the value of an indexed property</a> for a given index <var>index</var> in a
             <a href="#networkservices"><code>NetworkServices</code></a> object the user agent <em class="rfc2119"
             title="MUST">MUST</em> return the <a href="#networkservice"><code>NetworkService</code></a> object that
             represents the <var>index</var>th item in the collection.
        </p>
        <p>
          The <dfn id="dom-networkservices-getservicebyid"><code>getServiceById(id)</code></dfn> method <em class=
          "ct"><em class="rfc2119"
              title="MUST">MUST</em></em> return the first <a href="#networkservice"><code>NetworkService</code></a>
              object in the collection whose <a href="#dom-networkservice-id"><code>id</code></a> attribute is equal to
              the value of the <var>id</var> argument provided. When no <a href=
              "#networkservice"><code>NetworkService</code></a> objects match the given argument, the method <em class=
              "rfc2119"
             title="MUST">MUST</em> return null.
        </p>
      </section>
      <section id="events">
        <h3 aria-level="2"
            role="heading"
            id="h3_events">
          <span class="secno">6.3</span> Events
        </h3>
        <p>
          The following are the event handlers (and their corresponding event handler event types) that <em class=
          "ct"><em class="rfc2119"
              title="MUST">MUST</em></em> be supported, as IDL attributes, by all objects implementing the <a href=
              "#networkservices"><code>NetworkServices</code></a> interface:
        </p>
        <table border="1">
          <thead>
            <tr>
              <th>
                <span title="event handlers">Event handler</span>
              </th>
              <th>
                <span>Event handler event type</span>
              </th>
            </tr>
          </thead>
          <tbody>
            <tr>
              <td>
                <dfn id="dom-networkservices-onservicefound"
                    title="dom-NetworkServices-onservicefound"><code>onservicefound</code></dfn>
              </td>
              <td>
                <a href="#event-servicefound"><code>servicefound</code></a>
              </td>
            </tr>
            <tr>
              <td>
                <dfn id="dom-networkservices-onservicelost"
                    title="dom-NetworkServices-onservicelost"><code>onservicelost</code></dfn>
              </td>
              <td>
                <a href="#event-servicelost"><code>servicelost</code></a>
              </td>
            </tr>
          </tbody>
        </table>
      </section>
    </section>
    <section id="communicating-with-a-networked-service">
      <h2 aria-level="1"
          role="heading"
          id="h2_communicating-with-a-networked-service">
        <span class="secno">7.</span> Communicating with a networked service
      </h2>
      <p>
        The <a href="#networkservice"><code>NetworkService</code></a> interface is used to provide a set of connection
        information for an <abbr title="Hypertext Transfer Protocol">HTTP</abbr> service endpoint and if available,
        service events, running on a networked device.
      </p>
      <pre class="widl">
[NoInterfaceObject]
interface <dfn id="networkservice">NetworkService</dfn> {
  readonly attribute DOMString        <a href="#dom-networkservice-id">id</a>;
  readonly attribute DOMString        <a href="#dom-networkservice-name">name</a>;
  readonly attribute DOMString        <a href="#dom-networkservice-type">type</a>;
  readonly attribute DOMString        <a href="#dom-networkservice-url">url</a>;
  readonly attribute DOMString        <a href="#dom-networkservice-config">config</a>;

  readonly attribute boolean          <a href="#dom-networkservice-online">online</a>;

  // event handler attributes
           attribute <a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#eventhandler"
     class="externalDFN">EventHandler</a>     <a href="#dom-networkservice-onavailable">onavailable</a>;
           attribute <a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#eventhandler"
     class="externalDFN">EventHandler</a>     <a href="#dom-networkservice-onunavailable">onunavailable</a>;

           attribute <a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#eventhandler"
     class="externalDFN">EventHandler</a>     <a href="#dom-networkservice-onnotify">onnotify</a>;
};

<a href="#networkservice">NetworkService</a> implements <a href=
"http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#interface-eventtarget"
     class="externalDFN">EventTarget</a>;
</pre>
      <section id="attributes-1">
        <h3 aria-level="2"
            role="heading"
            id="h3_attributes-1">
          <span class="secno">7.1</span> Attributes
        </h3>
        <dl class="domintro">
          <dt>
            <var title="">service</var> . <code title="dom-networkservice-id"><a href=
            "#dom-networkservice-id">id</a></code>
          </dt>
          <dd>
            <p>
              A unique identifier for the given user-selected service instance.
            </p>
          </dd>
          <dt>
            <var title="">service</var> . <code title="dom-networkservice-name"><a href=
            "#dom-networkservice-name">name</a></code>
          </dt>
          <dd>
            <p>
              The name of the user-selected service.
            </p>
          </dd>
          <dt>
            <var title="">service</var> . <code title="dom-networkservice-type"><a href=
            "#dom-networkservice-type">type</a></code>
          </dt>
          <dd>
            <p>
              The <a href="#dfn-valid-service-type"
                 class="internalDFN">valid service type</a> token value of the user-selected service.
            </p>
          </dd>
          <dt>
            <var title="">service</var> . <code title="dom-networkservice-url"><a href=
            "#dom-networkservice-url">url</a></code>
          </dt>
          <dd>
            <p>
              The control URL endpoint (including any required port information) of the user-selected control service.
            </p>
          </dd>
          <dt>
            <var title="">service</var> . <code title="dom-networkservice-config"><a href=
            "#dom-networkservice-config">config</a></code>
          </dt>
          <dd>
            <p>
              The configuration information associated with the service depending on the requested service type.
            </p>
          </dd>
        </dl>
        <p>
          The <dfn id="dom-networkservice-id"><code>id</code></dfn> attribute is a unique identifier for the service.
          The same service provided at different times or on different objects <em class="rfc2119"
             title="MUST">MUST</em> have the same <a href="#dom-networkservice-id"><code>id</code></a> value.
        </p>
        <p>
          The <dfn id="dom-networkservice-name"><code>name</code></dfn> attribute represents a human-readable title for
          the service.
        </p>
        <p>
          The <dfn id="dom-networkservice-type"><code>type</code></dfn> attribute reflects the value of the <a href=
          "#dfn-valid-service-type"
             class="internalDFN">valid service type</a> of the service.
        </p>
        <p>
          The <dfn id="dom-networkservice-url"><code>url</code></dfn> attribute is an <a href=
          "http://url.spec.whatwg.org/#concept-absolute-url"
             class="externalDFN">absolute URL</a> pointing to the root <abbr title=
             "Hypertext Transfer Protocol">HTTP</abbr> endpoint for the service. Web pages can subsequently use this
             value for implicit cross-document messaging via various existing mechanisms (e.g. Web Sockets, Server-Sent
             Events, Web Messaging, XMLHttpRequest).
        </p>
        <p>
          The <dfn id="dom-networkservice-config"><code>config</code></dfn> attribute provides the raw configuration
          information extracted from the given network service.
        </p>
      </section>
      <section id="states">
        <h3 aria-level="2"
            role="heading"
            id="h3_states">
          <span class="secno">7.2</span> States
        </h3>
        <dl class="domintro">
          <dt>
            <var title="">service</var> . <code title="dom-networkservice-online"><a href=
            "#dom-networkservice-online">online</a></code>
          </dt>
          <dd>
            <p>
              Returns <code>true</code> if the service is reporting that it is accessible on the local network or
              <code>false</code> if the service is no longer accessible (temporarily or permanently) on the local
              network.
            </p>
          </dd>
        </dl>
        <p>
          The <dfn id="dom-networkservice-online"><code>online</code></dfn> attribute indicates whether the service is
          either <var>online</var>, and therefore accessible on the local network, in which case this attribute will
          return <code>true</code> or, <var>offline</var>, and therefore not accessible on the local network, either
          temporarily or permanently, in which case this attribute will return <code>false</code>. This attribute
          <em class="rfc2119"
             title="MUST">MUST</em> default to <code>true</code>.
        </p>
      </section>
      <section id="events-1">
        <h3 aria-level="2"
            role="heading"
            id="h3_events-1">
          <span class="secno">7.3</span> Events
        </h3>
        <p>
          The following are the event handlers (and their corresponding event handler event types) that <em class=
          "ct"><em class="rfc2119"
              title="MUST">MUST</em></em> be supported, as IDL attributes, by all objects implementing the <a href=
              "#networkservice"><code>NetworkService</code></a> interface:
        </p>
        <table border="1">
          <thead>
            <tr>
              <th>
                <span title="event handlers">Event handler</span>
              </th>
              <th>
                <span>Event handler event type</span>
              </th>
            </tr>
          </thead>
          <tbody>
            <tr>
              <td>
                <dfn id="dom-networkservice-onnotify"
                    title="dom-NetworkService-onnotify"><code>onnotify</code></dfn>
              </td>
              <td>
                <a href="#event-notify"><code>notify</code></a>
              </td>
            </tr>
            <tr>
              <td>
                <dfn id="dom-networkservice-onavailable"
                    title="dom-NetworkService-onavailable"><code>onavailable</code></dfn>
              </td>
              <td>
                <a href="#event-available"><code>available</code></a>
              </td>
            </tr>
            <tr>
              <td>
                <dfn id="dom-networkservice-onunavailable"
                    title="dom-NetworkService-onunavailable"><code>onunavailable</code></dfn>
              </td>
              <td>
                <a href="#event-unavailable"><code>unavailable</code></a>
              </td>
            </tr>
          </tbody>
        </table>
      </section>
    </section>
    <section id="service-discovery">
      <h2 aria-level="1"
          role="heading"
          id="h2_service-discovery">
        <span class="secno">8.</span> Service Discovery
      </h2>
      <p>
        A <a href="#dfn-user-agent"
           class="internalDFN">user agent</a> conforming to this specification <em class="rfc2119"
           title="MAY">MAY</em> implement <abbr title="Simple Service Discovery Protocol">SSDP</abbr> [<cite><a class=
           "bibref"
           href="#bib-UPNP-DEVICEARCH11">UPNP-DEVICEARCH11</a></cite>], Zeroconf [<cite><a class="bibref"
           href="#bib-DNS-SD">DNS-SD</a></cite>] + [<cite><a class="bibref"
           href="#bib-MDNS">MDNS</a></cite>] and/or <abbr title="Discovery and Launch Protocol">DIAL</abbr> [<a href=
           "https://sites.google.com/a/dial-multiscreen.org/dial/dial-protocol-specification"><abbr title=
           "Discovery and Launch Protocol">DIAL</abbr></a>] <dfn id="dfn-service-discovery-mechanisms">service
           discovery mechanisms</dfn> - the requirements detailed in this section of the specification - to enable Web
           pages to request and connect with <abbr title="Hypertext Transfer Protocol">HTTP</abbr> services running on
           networked devices, discovered via any of these mechanisms, through this <abbr title=
           "Application Programming Interface">API</abbr>. When a <a href="#dfn-user-agent"
           class="internalDFN">user agent</a> implements any of these <a href="#dfn-service-discovery-mechanisms"
           class="internalDFN">service discovery mechanisms</a>, then it <em class="rfc2119"
           title="MUST">MUST</em> conform to the corresponding algorithms provided in this section of the
           specification.
      </p>
      <p>
        This section presents how the results of these <a href="#dfn-service-discovery-mechanisms"
           class="internalDFN">service discovery mechanisms</a> will be matched to requested service types, how the
           user agent stores available and active services and how their properties are applied to any resulting
           <a href="#networkservice"><code>NetworkService</code></a> objects.
      </p>
      <p>
        It is expected that user agents will perform these <a href="#dfn-service-discovery-mechanisms"
           class="internalDFN">service discovery mechanisms</a> asynchronously and periodically update the <a href=
           "#dfn-list-of-available-service-records"
           class="internalDFN">list of available service records</a> as required. The timing of any <a href=
           "#dfn-service-discovery-mechanisms"
           class="internalDFN">service discovery mechanisms</a> is an implementation detail left to the discretion of
           the implementer (e.g. by continuously monitoring the network as a background process or on invocation of
           this <abbr title="Application Programming Interface">API</abbr> from a Web page).
      </p>
      <p>
        The <dfn id="dfn-list-of-available-service-records">list of available service records</dfn> is a single dynamic
        internal lookup table within user agents that is used to track all the services that have been discovered and
        are available in the current network at the current time. At any point during the running of any of the
        <a href="#dfn-service-discovery-mechanisms"
           class="internalDFN">service discovery mechanisms</a> then existing entries within this table can be updated,
           entries can be added and entries can be removed as the status of networked services changes according to the
           rules defined in this specification.
      </p>
      <p>
        The <dfn id="dfn-list-of-active-service-managers">list of active service managers</dfn> is an internal list
        within user agents that is used to track all <a href="#networkservices"><code>NetworkServices</code></a>
        objects currently being shared with any web pages at the current time within the user agent. Each <a href=
        "#networkservices"><code>NetworkServices</code></a> object in the <a href=
        "#dfn-list-of-active-service-managers"
           class="internalDFN">list of active service managers</a> represents a collection of zero or more <a href=
           "#networkservice"><code>NetworkService</code></a> objects - known as its <dfn id=
           "dfn-indexed-properties">indexed properties</dfn>. <a href="#networkservice"><code>NetworkService</code></a>
           objects are attached as the <a href="#dfn-indexed-properties"
           class="internalDFN">indexed properties</a> of a <a href="#networkservices"><code>NetworkServices</code></a>
           object as part of the <a href="#dom-navigator-getnetworkservices"><code>getNetworkServices()</code></a>
           algorithm.
      </p>
      <p>
        The rule for <dfn id="dfn-adding-an-available-service">adding an available service</dfn> is the process of
        adding a <a href="#dfn-new-service"
           class="internalDFN">new service</a> or updating an <a href="#dfn-existing-service"
           class="internalDFN">existing service</a> that is generally available on the user's current network in the
           <a href="#dfn-list-of-available-service-records"
           class="internalDFN">list of available service records</a>. This rule takes one argument, <var>network
           service record</var>, and consists of running the following steps:
      </p>
      <ol class="rule">
        <li>For each <var>existing service record</var> in the current <a href="#dfn-list-of-available-service-records"
              class="internalDFN">list of available service records</a>, run the following sub-steps:
          <ol class="rule">
            <li>If the <var>existing service record</var>'s <code>id</code> property does not equal <var>network
            service record</var>'s <code>id</code> property then abort any remaining sub-steps and continue at the next
            available <var>existing service record</var>.
            </li>
            <li>Replace the value of <var>existing service record</var> in the current <a href=
            "#dfn-list-of-available-service-records"
                  class="internalDFN">list of available service records</a> with the value of <var>network service
                  record</var>, aborting any remaining steps in this algorithm and return.
            </li>
          </ol>
        </li>
        <li>Add <var>network service record</var> to the <a href="#dfn-list-of-available-service-records"
              class="internalDFN">list of available service records</a> as a new item.
        </li>
        <li>For each <var>service manager</var> in the <a href="#dfn-list-of-active-service-managers"
              class="internalDFN">list of active service managers</a> run the following steps:
          <ol class="rule">
            <li>For each <var>active service</var> in <var>service manager</var> run the following steps:
              <ol class="rule">
                <li>If the <var>network service record</var>'s <code>id</code> property equals the <var>active
                service</var>'s <code>id</code> attribute and <var>active service</var>'s <code>online</code> attribute
                is currently set to <code>false</code> then set <var>active service</var>'s <a href=
                "#dom-networkservice-online"><code>online</code></a> attribute to <code>true</code> and then <a href=
                "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
                      class="externalDFN">queue a task</a> to dispatch a newly created event with the name <a href=
                      "#event-available"><code>available</code></a> that uses the <a href=
                      "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
                      class="externalDFN"><code>Event</code></a> interface, which does not bubble, is not cancellable,
                      and has no default action, at the current <var>active service</var> object.
                </li>
              </ol>
            </li>
            <li>Let <var>'service type in current service manager' flag</var> be <code>false</code>.
            </li>
            <li>For each <var>requested control type</var> of the <var>requested control types</var> in <var>service
            manager</var> run the following steps:
              <ol class="rule">
                <li>If <var>network service record</var>'s <code>type</code> property does not equal <var>requested
                control type</var> then abort any remaining sub-steps and continue at the next available <var>requested
                control type</var>.
                </li>
                <li>Set the <var>'service type in current service manager' flag</var> to <code>true</code>, abort any
                remaining sub-steps and continue.
                </li>
              </ol>
            </li>
            <li>If the <var>'service type in current service manager' flag</var> is set to <code>true</code> then
            increment <var>service manager</var>'s <a href=
            "#dom-networkservices-servicesavailable"><code>servicesAvailable</code></a> attribute by <code>1</code> and
            then <a href="http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
                  class="externalDFN">queue a task</a> to dispatch a newly created event with the name <a href=
                  "#event-servicefound"><code>servicefound</code></a> that uses the <a href=
                  "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
                  class="externalDFN"><code>Event</code></a> interface, which does not bubble, is not cancellable, and
                  has no default action, at the current <var>service manager</var> object.
            </li>
          </ol>
        </li>
      </ol>
      <p>
        The rule for <dfn id="dfn-removing-an-available-service">removing an available service</dfn> is the general
        process of removing an <a href="#dfn-existing-service"
           class="internalDFN">existing service</a> from the <a href="#dfn-list-of-available-service-records"
           class="internalDFN">list of available service records</a> that has left the user's current network or has
           otherwise expired. This rule takes one argument, <var>service identifier</var>, and consists of running the
           following steps:
      </p>
      <ol class="rule">
        <li>For each <var>existing service record</var> in the current <a href="#dfn-list-of-available-service-records"
              class="internalDFN">list of available service records</a>, run the following sub-steps:
          <ol class="rule">
            <li>If the <var>existing service record</var>'s <code>id</code> property does not match <var>service
            identifier</var> then skip any remaining sub-steps for the current <var>existing service record</var> and
            continue at the next available <var>existing service record</var>.
            </li>
            <li>Let <var>'service type in use' flag</var> be <code>false</code>.
            </li>
            <li>For each <var>service manager</var> in the <a href="#dfn-list-of-active-service-managers"
                  class="internalDFN">list of active service managers</a> run the following steps:
              <ol class="rule">
                <li>Let <var>'service type in current service manager' flag</var> be <code>false</code>.
                </li>
                <li>For each <var>active service</var> in <var>service manager</var> run the following steps:
                  <ol class="rule">
                    <li>If <var>existing service record</var>'s <code>id</code> property equals the <var>active
                    service</var>'s <code>id</code> attribute and <var>active service</var>'s <a href=
                    "#dom-networkservice-online"><code>online</code></a> attribute is currently set to
                    <code>true</code> then set <var>active service</var>'s <a href="#dom-networkservice-online"><code>
                      online</code></a> attribute to <code>false</code> and then <a href=
                      "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
                          class="externalDFN">queue a task</a> to dispatch a newly created event with the name <a href=
                          "#event-unavailable"><code>unavailable</code></a> that uses the <a href=
                          "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
                          class="externalDFN"><code>Event</code></a> interface, which does not bubble, is not
                          cancellable, and has no default action, at the current <var>active service</var>.
                    </li>
                  </ol>
                </li>
                <li>For each <var>requested control type</var> of the <var>requested control types</var> in
                <var>service manager</var> run the following steps:
                  <ol class="rule">
                    <li>If <var>existing service record</var>'s <code>type</code> property does not equal
                    <var>requested control type</var> then abort any remaining sub-steps and continue at the next
                    available <var>requested control type</var>.
                    </li>
                    <li>Set the <var>'service type in current service manager' flag</var> to <code>true</code> and the
                    <var>'service type in use' flag</var> to <code>true</code>, abort any remaining sub-steps and
                    continue.
                    </li>
                  </ol>
                </li>
                <li>If the <var>'service type in current service manager' flag</var> is set to <code>true</code> then
                decrement <var>service manager</var>'s <a href=
                "#dom-networkservices-servicesavailable"><code>servicesAvailable</code></a> attribute by <code>1</code>
                and then <a href=
                "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
                      class="externalDFN">queue a task</a> to dispatch a newly created event with the name <a href=
                      "#event-servicelost"><code>servicelost</code></a> that uses the <a href=
                      "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
                      class="externalDFN"><code>Event</code></a> interface, which does not bubble, is not cancellable,
                      and has no default action, at the current <var>service manager</var> object.
                </li>
              </ol>
            </li>
            <li>If the <var>'service type in use' flag</var> is <code>false</code> and the <var>existing service
            record</var>'s <code>type</code> property begins with the DOMString "<code>upnp:</code>" and <var>existing
            service record</var>'s <code>eventsURL</code> property is set then run the rule to <a href=
            "#dfn-terminate-an-existing-upnp-events-subscription"
                  class="internalDFN">terminate an existing UPnP Events Subscription</a>, if one is currently active
                  (as a result of having previously called <a href="#dfn-setup-a-upnp-events-subscription"
                  class="internalDFN">setup a UPnP Events Subscription</a> against the current <var>existing service
                  record</var>).
            </li>
            <li>Remove <var>existing service record</var> from the current <a href=
            "#dfn-list-of-available-service-records"
                  class="internalDFN">list of available service records</a>.
            </li>
          </ol>
        </li>
      </ol>
      <p>
        User agents <em class="rfc2119"
           title="SHOULD">SHOULD</em> expire a service record from the <a href="#dfn-list-of-available-service-records"
           class="internalDFN">list of available service records</a> when its <code>expiryTimestamp</code> attribute
           exceeds the current UTC timestamp. When this condition is met the <a href="#dfn-user-agent"
           class="internalDFN">user agent</a> <em class="rfc2119"
           title="SHOULD">SHOULD</em> run the rule for <a href="#dfn-removing-an-available-service"
           class="internalDFN">removing an available service</a>, passing in the expired service record's
           <code>id</code> attribute as the only argument.
      </p>
      <section id="zeroconf-mdns-dns-sd">
        <h3 aria-level="2"
            role="heading"
            id="h3_zeroconf-mdns-dns-sd">
          <span class="secno">8.1</span> Zeroconf (<abbr title="Multicast DNS">mDNS</abbr> + <abbr title=
          "Domain Name System">DNS</abbr>-<abbr title="Service Discovery">SD</abbr>)
        </h3>
        <p>
          For each <abbr title="Domain Name System">DNS</abbr> response received from a user-agent-initiated Multicast
          <abbr title="Domain Name System">DNS</abbr> Browse for <abbr title="DNS Pointer Record">PTR</abbr> records
          with the name <code>_services._dns-sd._udp</code> on the resolved recommended automatic browsing domain
          [<cite><a class="bibref"
             href="#bib-MDNS">MDNS</a></cite>], the <a href="#dfn-user-agent"
             class="internalDFN">user agent</a> <em class="rfc2119"
             title="MUST">MUST</em> run the following steps:
        </p>
        <ol class="rule">
          <li>Let <var>service <abbr title="Multicast DNS">mDNS</abbr> responses</var> be an array of <abbr title=
          "DNS Pointer Record">PTR</abbr> records received by issuing a Multicast <abbr title=
          "Domain Name System">DNS</abbr> Browse for <abbr title="DNS Pointer Record">PTR</abbr> records with the name
          of the current discovered service type.
          </li>
          <li>For each Object <var>service <abbr title="Multicast DNS">mDNS</abbr> response</var> in <var>service
          <abbr title="Multicast DNS">mDNS</abbr> responses</var>, run the following steps:
            <ol>
              <li>Let <var>network service record</var> be an Object consisting of the following empty properties:
              <code>id</code>, <code>name</code>, <code>type</code>, <code>url</code>, <code>config</code>,
              <code>expiryTimestamp</code>.
              </li>
              <li>Set <var>network service record</var>'s <code>id</code> property to the value of the full
                <abbr title="DNS Pointer Record">PTR</abbr> Service Instance Name [<cite><a class="bibref"
                   href="#bib-MDNS">MDNS</a></cite>].
              </li>
              <li>Set <var>network service record</var>'s <code>name</code> property to the value of the <abbr title=
              "DNS Pointer Record">PTR</abbr> Service Instance Name's <var>Instance</var> component [<cite><a class=
              "bibref"
                   href="#bib-MDNS">MDNS</a></cite>].
              </li>
              <li>Set <var>network service record</var>'s <code>type</code> property to the concatenation of the string
              <code>zeroconf:</code> followed be the value of the <abbr title="DNS Pointer Record">PTR</abbr> Service
              Instance Name's <var>Service</var> component [<cite><a class="bibref"
                   href="#bib-MDNS">MDNS</a></cite>].
              </li>
              <li>Set <var>network service record</var>'s <code>url</code> property to the resolvable Service URL
              obtained from performing an <abbr title="Domain Name System">DNS</abbr>-<abbr title=
              "Service Discovery">SD</abbr> Lookup [<cite><a class="bibref"
                   href="#bib-DNS-SD">DNS-SD</a></cite>] of the current service from the <abbr title=
                   "DNS Pointer Record">PTR</abbr> record provided [<cite><a class="bibref"
                   href="#bib-MDNS">MDNS</a></cite>].
              </li>
              <li>Set <var>network service record</var>'s <code>config</code> property to the string value of the
              contents of the first <abbr title="Domain Name System">DNS</abbr>-<abbr title=
              "Service Discovery">SD</abbr> TXT record associated with the <var>service <abbr title=
              "Multicast DNS">mDNS</abbr> response</var> as defined in [<cite><a class="bibref"
                   href="#bib-DNS-SD">DNS-SD</a></cite>].
              </li>
              <li>Set <var>network service record</var>'s <code>expiryTimestamp</code> property to the value of the
              current date, in UTC timestamp format, plus a value of <code>120</code> seconds.
              </li>
              <li>Run the general rule for <a href="#dfn-adding-an-available-service"
                    class="internalDFN">adding an available service</a>, passing in the current <var>network service
                    record</var> as the only argument.
              </li>
            </ol>
          </li>
        </ol>
      </section>
      <section id="simple-service-discovery-protocol-ssdp">
        <h3 aria-level="2"
            role="heading"
            id="h3_simple-service-discovery-protocol-ssdp">
          <span class="secno">8.2</span> Simple Service Discovery Protocol (<abbr title=
          "Simple Service Discovery Protocol">SSDP</abbr>)
        </h3>
        <p>
          A user agent that implements UPnP service discovery <em class="rfc2119"
             title="MUST">MUST</em> issue a <dfn id="dfn-search-request-for-upnp-root-devices">search request for UPnP
             root devices</dfn> against the user's current local network according to the full normative text and
             timing provided in 'Section 1.3.2: Search request with M-SEARCH' detailed in [<cite><a class="bibref"
             href="#bib-UPNP-DEVICEARCH11">UPNP-DEVICEARCH11</a></cite>].
        </p>
        <p>
          The user agent <em class="rfc2119"
             title="MUST">MUST</em> issue all <a title="search request for UPnP root devices"
             href="#dfn-search-request-for-upnp-root-devices"
             class="internalDFN">search requests for UPnP root devices</a> with a <abbr title=
             "Hypertext Transfer Protocol">HTTP</abbr> request line equal to <code>M-SEARCH * <abbr title=
             "Hypertext Transfer Protocol">HTTP</abbr>/1.1</code>, with a HOST header equal to the reserved multicast
             address and port of <code>239.255.255.250:1900</code> and a MAN header equal to
             <code>ssdp:discover</code>. The <a href="#dfn-user-agent"
             class="internalDFN">user agent</a> must also send an ST header with this <abbr title=
             "Hypertext Transfer Protocol">HTTP</abbr> request equal to the String value of <code>ssdp:all</code> or
             <code>upnp:rootdevice</code> or a single <a href="#dfn-valid-service-type"
             class="internalDFN">valid service type</a> token beginning with the String value <code>upnp:</code>. If a
             single <a href="#dfn-valid-service-type"
             class="internalDFN">valid service type</a> token beginning with the String value <code>upnp:</code> is to
             be used, the user agent <em class="rfc2119"
             title="MUST">MUST</em> strip the leading String <code>upnp:</code> before using this value in this
             <abbr title="Hypertext Transfer Protocol">HTTP</abbr> request. The user-agent <em class="rfc2119"
             title="MUST">MUST</em> also send an MX header equal to a <dfn id=
             "dfn-maximum-upnp-advertisement-response-wait-time">maximum UPnP advertisement response wait time</dfn>
             value between <code>1</code> and <code>5</code> seconds with this <abbr title=
             "Hypertext Transfer Protocol">HTTP</abbr> request.
        </p>
        <p>
          The user agent <em class="rfc2119"
             title="MUST">MUST</em> listen for any incoming responses to any <a href=
             "#dfn-search-request-for-upnp-root-devices"
             class="internalDFN">search request for UPnP root devices</a>.
        </p>
        <p>
          For each <dfn id="dfn-http-response"><abbr title="Hypertext Transfer Protocol">HTTP</abbr> Response</dfn>
          following an initial <a href="#dfn-search-request-for-upnp-root-devices"
             class="internalDFN">search request for UPnP root devices</a> sent on a <a href=
             "#dfn-standard-upnp-address-and-port"
             class="internalDFN">standard UPnP address and port</a> the user agent <em class="rfc2119"
             title="MUST">MUST</em> run the following steps:
        </p>
        <ol class="rule">
          <li>If the <a href="#dfn-http-response"
                class="internalDFN"><abbr title="Hypertext Transfer Protocol">HTTP</abbr> Response</a> is not a
                <abbr title="Hypertext Transfer Protocol">HTTP</abbr> 200 OK response then this response is invalid and
                the user agent <em class="rfc2119"
                title="MUST">MUST</em> discard this response, abort any remaining steps and return. The user agent
                <em class="rfc2119"
                title="MAY">MAY</em> issue a new <a href="#dfn-search-request-for-upnp-root-devices"
                class="internalDFN">search request for UPnP root devices</a> as a result of this error occurring.
          </li>
          <li>If the <a href="#dfn-maximum-upnp-advertisement-response-wait-time"
                class="internalDFN">maximum UPnP advertisement response wait time</a> has been exceeded since the
                initial <a href="#dfn-search-request-for-upnp-root-devices"
                class="internalDFN">search request for UPnP root devices</a> was sent then the <a href=
                "#dfn-http-response"
                class="internalDFN"><abbr title="Hypertext Transfer Protocol">HTTP</abbr> Response</a> is invalid and
                the user agent <em class="rfc2119"
                title="MUST">MUST</em> discard this response, abort any remaining steps and return. The user agent
                <em class="rfc2119"
                title="MAY">MAY</em> stop listening for responses from the current <a href=
                "#dfn-search-request-for-upnp-root-devices"
                class="internalDFN">search request for UPnP root devices</a> as a result of this error occurring.
                Equally, the user agent <em class="rfc2119"
                title="MAY">MAY</em> issue a new <a href="#dfn-search-request-for-upnp-root-devices"
                class="internalDFN">search request for UPnP root devices</a> as a result of this error occurring.
          </li>
          <li>Let <var>ssdp device</var> be an Object with a property for each <abbr title=
          "Hypertext Transfer Protocol">HTTP</abbr> header received in the <a href="#dfn-http-response"
                class="internalDFN"><abbr title="Hypertext Transfer Protocol">HTTP</abbr> Response</a>, with each key
                being the name of a <abbr title="Hypertext Transfer Protocol">HTTP</abbr> response header and each
                value being that <abbr title="Hypertext Transfer Protocol">HTTP</abbr> response header's value.
          </li>
          <li>If <var>ssdp device</var> does not contain at least one <var>CACHE-CONTROL</var> entry, at least one
          <var>USN</var> entry, at least one <var>ST</var> entry and at least one <var>LOCATION</var> entry then the
          <a href="#dfn-http-response"
                class="internalDFN"><abbr title="Hypertext Transfer Protocol">HTTP</abbr> Response</a> is invalid and
                the <a href="#dfn-user-agent"
                class="internalDFN">user agent</a> <em class="rfc2119"
                title="MUST">MUST</em> discard this response, abort any remaining steps and return.
          </li>
          <li>The user agent <em class="rfc2119"
                title="MUST">MUST</em> run the rule for <a href="#dfn-obtaining-a-upnp-device-description-file"
                class="internalDFN">obtaining a UPnP Device Description File</a> passing in the first occurrence of
                <var>LOCATION</var> from <var>ssdp device</var> as the <var>device descriptor URL</var> argument and
                the first occurrence of <var>USN</var> from <var>ssdp device</var> as the <var>device identifier</var>
                argument and the first occurrence of <var>CACHE-CONTROL</var> from <var>ssdp device</var> (minus the
                leading string of <code>max-age=</code>) as the <var>device expiry</var> argument.
          </li>
        </ol>
        <p>
          The user agent <em class="rfc2119"
             title="MUST">MUST</em> listen for incoming requests on the <dfn id=
             "dfn-standard-upnp-address-and-port">standard UPnP address and port</dfn> on all current local network
             interface addresses with the port <code>1900</code>.
        </p>
        <p>
          For each <dfn id="dfn-http-request"><abbr title="Hypertext Transfer Protocol">HTTP</abbr> Request</dfn>
          received on a <a href="#dfn-standard-upnp-address-and-port"
             class="internalDFN">standard UPnP address and port</a> the user agent <em class="rfc2119"
             title="MUST">MUST</em> run the following steps:
        </p>
        <ol class="rule">
          <li>If the <a href="#dfn-http-request"
                class="internalDFN"><abbr title="Hypertext Transfer Protocol">HTTP</abbr> Request</a> is not a
                <abbr title="Hypertext Transfer Protocol">HTTP</abbr> NOTIFY request then it is not a valid UPnP
                Request and the user agent <em class="rfc2119"
                title="MUST">MUST</em> discard this request, abort any remaining steps and return.
          </li>
          <li>Let <var>ssdp device</var> be an Object with a property for each <abbr title=
          "Hypertext Transfer Protocol">HTTP</abbr> header received in the <a href="#dfn-http-request"
                class="internalDFN"><abbr title="Hypertext Transfer Protocol">HTTP</abbr> Request</a>, with each key
                being the name of a <abbr title="Hypertext Transfer Protocol">HTTP</abbr> header and each value being
                that <abbr title="Hypertext Transfer Protocol">HTTP</abbr> header's value.
          </li>
          <li>If <var>ssdp device</var>'s <var>NTS</var> entry is equal to <code>ssdp:alive</code> and the <a href=
          "#dfn-http-request"
                class="internalDFN"><abbr title="Hypertext Transfer Protocol">HTTP</abbr> Request</a> does not contain
                at least one <var>CACHE-CONTROL</var> entry, at least one <var>USN</var> entry, at least one
                <var>NT</var> entry, at least one <var>NTS</var> entry and at least one <var>LOCATION</var> entry, then
                the <a href="#dfn-user-agent"
                class="internalDFN">user agent</a> <em class="rfc2119"
                title="MUST">MUST</em> discard this request, abort any remaining steps and return.
          </li>
          <li>If <var>ssdp device</var>'s <var>NTS</var> entry is equal to <code>ssdp:alive</code> then the user agent
          <em class="rfc2119"
                title="MUST">MUST</em> run the rule for <a href="#dfn-obtaining-a-upnp-device-description-file"
                class="internalDFN">obtaining a UPnP Device Description File</a> passing in the first occurrence of
                <var>LOCATION</var> from <var>ssdp device</var> as the <var>device descriptor URL</var> argument and
                the first occurrence of <var>USN</var> from <var>ssdp device</var> as the <var>device identifier</var>
                argument and the first occurrence of <var>CACHE-CONTROL</var> from <var>ssdp device</var> (minus the
                leading string of <code>max-age=</code>) as the <var>device expiry</var>.<br>
            <br>
            Otherwise, if <var>ssdp device</var>'s <var>NTS</var> entry is equal to <code>ssdp:byebye</code> then the
            user agent <em class="rfc2119"
                title="MUST">MUST</em> run the rule for <a href=
                "#dfn-removing-all-services-from-a-registered-upnp-device"
                class="internalDFN">removing all services from a registered UPnP Device</a> passing in the first
                occurrence of <var>USN</var> from <var>ssdp device</var> as the <var>device identifier</var> argument.
          </li>
        </ol>
        <p>
          The rule for <dfn id="dfn-obtaining-a-upnp-device-description-file">obtaining a UPnP Device Description
          File</dfn> is the process of obtaining the contents of a standard UPnP Device Description [<cite><a class=
          "bibref"
             href="#bib-UPNP-DEVICEARCH11">UPNP-DEVICEARCH11</a></cite>] from a URL-based resource. This rule takes
             three arguments - <var>device descriptor URL</var>, <var>device identifier</var> and <var>device
             expiry</var> - and when called the user agent <em class="rfc2119"
             title="MUST">MUST</em> run the following steps:
        </p>
        <ol class="rule">
          <li>Let <var>device descriptor file</var> contain the contents of the file located at the URL provided in
          <var>device descriptor URL</var> obtained according to the rules defined in 'Section 2.11: Retrieving a
          description using <abbr title="Hypertext Transfer Protocol">HTTP</abbr>' in [<cite><a class="bibref"
               href="#bib-UPNP-DEVICEARCH11">UPNP-DEVICEARCH11</a></cite>].
          </li>
          <li>If the value provided in <var>device descriptor URL</var> cannot be resolved as a reachable URL on the
          current network or the <var>device descriptor file</var> remains empty then it is invalid and the <a href=
          "#dfn-user-agent"
                class="internalDFN">user agent</a> <em class="rfc2119"
                title="MUST">MUST</em> abort any remaining steps and return.
          </li>
          <li>Run the rule for <a href="#dfn-processing-a-upnp-device-description-file"
                class="internalDFN">processing a UPnP Device Description File</a>, passing in the current <var>device
                descriptor file</var>, <var>device identifier</var> and <var>device expiry</var> arguments.
          </li>
        </ol>
        <p>
          The rule for <dfn id="dfn-processing-a-upnp-device-description-file">processing a UPnP Device Description
          File</dfn> is the process of parsing the contents of a standard UPnP Device Description [<cite><a class=
          "bibref"
             href="#bib-UPNP-DEVICEARCH11">UPNP-DEVICEARCH11</a></cite>] and registering the UPnP services contained
             therein within the <a href="#dfn-list-of-available-service-records"
             class="internalDFN">list of available service records</a>.
        </p>
        <p>
          The rule for <a href="#dfn-processing-a-upnp-device-description-file"
             class="internalDFN">processing a UPnP Device Description File</a> takes three arguments - <var>device
             descriptor file</var>, <var>device identifier</var> and <var>device expiry</var> - and when called the
             user agent <em class="rfc2119"
             title="MUST">MUST</em> run the following steps:
        </p>
        <ol class="rule">
          <li>Let <var>advertised services</var> be a list of all advertised services obtained from the <var>device
          descriptor file</var> containing the value of the first occurrence of the <code>&lt;serviceList&gt;</code>
          element as it is defined in 'Section 2.3: Device Description' in [<cite><a class="bibref"
               href="#bib-UPNP-DEVICEARCH11">UPNP-DEVICEARCH11</a></cite>].
          </li>
          <li>For each <code>&lt;service&gt;</code> element - known as an <var>advertised service</var> - in
          <var>advertised services</var> run the following steps:
            <ol class="rule">
              <li>Let <var>network service record</var> be a new Object consisting of the following empty properties:
              <code>id</code>, <code>deviceId</code>, <code>name</code>, <code>type</code>, <code>url</code>,
              <code>eventsUrl</code>, <code>config</code>, <code>expiryTimestamp</code>.
              </li>
              <li>Set <var>network service record</var>'s <code>id</code> property to the concatenated string value of
              the first occurrence of the <code>&lt;UDN&gt;</code> element in the <var>device descriptor file</var>
              with the <var>advertised service</var>'s <code>&lt;serviceId&gt;</code> sub-element.
              </li>
              <li>Set <var>network service record</var>'s <code>deviceId</code> property to the value of <var>device
              identifier</var>.
              </li>
              <li>Set <var>network service record</var>'s <code>name</code> property to the string value of the first
              occurrence of the <var>advertised service</var>'s <code>&lt;serviceId&gt;</code> sub-element.
              </li>
              <li>Set <var>network service record</var>'s <code>type</code> property to the concatenation of the string
              <code>upnp:</code> followed by the string value of the first occurrence of the <var>advertised
              service</var>'s <code>&lt;serviceType&gt;</code> sub-element.
              </li>
              <li>Set <var>network service record</var>'s <code>url</code> property to the string value of the first
              occurrence of the <var>advertised service</var>'s <code>&lt;controlURL&gt;</code> sub-element.
              </li>
              <li>Set <var>network service record</var>'s <code>config</code> property to the string value of the
              contents of the first occurrence of the <code>&lt;device&gt;</code> element in the <var>device descriptor
              file</var>.
              </li>
              <li>If <var>advertised service</var>'s <code>&lt;eventSubURL&gt;</code> sub-element is not empty, then
              set <var>network service record</var>'s <code>eventsUrl</code> property to the string value of the first
              occurrence of the <var>advertised service</var>'s <code>&lt;eventSubURL&gt;</code> sub-element.
              Otherwise, do not set <var>network service record</var>'s <code>eventsUrl</code> property.
              </li>
              <li>Set <var>network service record</var>'s <code>expiryTimestamp</code> property to the value of the
              current date, in UTC timestamp format, plus the value of <var>device expiry</var>.
              </li>
              <li>Run the general rule for <a href="#dfn-adding-an-available-service"
                    class="internalDFN">adding an available service</a>, passing in the current <var>network service
                    record</var> as the only argument.
              </li>
            </ol>
          </li>
          <li>If <var>device descriptor file</var> contains a <code>&lt;deviceList&gt;</code> element then for each
          <code>&lt;device&gt;</code> element within <code>&lt;deviceList&gt;</code> - herein known as an <var>embedded
          device descriptor file</var> - the user agent <em class="rfc2119"
                title="MUST">MUST</em> run the rule for <a href="#dfn-processing-a-upnp-device-description-file"
                class="internalDFN">processing a UPnP Device Description File</a>, passing in the current <var>embedded
                device descriptor file</var> as the <var>device descriptor file</var> argument, along with the current
                <var>device identifier</var> and <var>device expiry</var> arguments.
          </li>
        </ol>
        <p>
          The rule for <dfn id="dfn-removing-all-services-from-a-registered-upnp-device">removing all services from a
          registered UPnP Device</dfn> is the process of removing all services associated with a device from the
          <a href="#dfn-list-of-available-service-records"
             class="internalDFN">list of available service records</a> that has left the user's current network or has
             otherwise timed out or expired. This rule takes one argument, <var>device identifier</var>, and consists
             of running the following steps:
        </p>
        <ol class="rule">
          <li>For each <var>existing service record</var> in the current <a href=
          "#dfn-list-of-available-service-records"
                class="internalDFN">list of available service records</a>, run the following sub-steps:
            <ol class="rule">
              <li>If the <var>existing service record</var>'s <code>deviceId</code> property does not match <var>device
              identifier</var> then skip any remaining sub-steps for the current <var>existing service record</var> and
              continue at the next available <var>existing service record</var>.
              </li>
              <li>Run the general rule for <a href="#dfn-removing-an-available-service"
                    class="internalDFN">removing an available service</a> passing in <var>existing service
                    record</var>'s <code>id</code> property as the only argument.
              </li>
            </ol>
          </li>
        </ol>
        <p>
          When the <a href="#dfn-user-agent"
             class="internalDFN">user agent</a> is to <dfn id="dfn-setup-a-upnp-events-subscription">setup a UPnP
             Events Subscription</dfn>, it is to run the following steps with the current <var>network service
             record</var> object as defined in 'Section 4.1.2: SUBSCRIBE with NT and CALLBACK' in [<cite><a class=
             "bibref"
             href="#bib-UPNP-DEVICEARCH11">UPNP-DEVICEARCH11</a></cite>]:
        </p>
        <ol class="rule">
          <li>If <var>network service record</var>'s <code>eventsUrl</code> property is empty then the <a href=
          "#dfn-user-agent"
                class="internalDFN">user agent</a> <em class="rfc2119"
                title="MUST">MUST</em> abort these steps.
          </li>
          <li>Let <var>callback URL</var> be the value of creating a new <a href=
          "#dfn-user-agent-generated-callback-url"
                class="internalDFN">user-agent generated callback url</a>.
          </li>
          <li>Send a <abbr title="Hypertext Transfer Protocol">HTTP</abbr> SUBSCRIBE request with a <em>NT</em> header
          with a string value of <code>upnp:event</code>, a <em>TIMEOUT</em> header with a user-agent defined timeout
          value (in the form <code>Second-XX</code> where <code>XX</code> is the user-agent defined timeout value in
          seconds) and a <em>CALLBACK</em> header with a string value of <var>callback URL</var> towards the
          <var>network service record</var>'s <code>eventsUrl</code> property.
          </li>
          <li>If a non-200 OK response is received from the <abbr title="Hypertext Transfer Protocol">HTTP</abbr>
          SUBSCRIBE request then the <a href="#dfn-user-agent"
                class="internalDFN">user agent</a> <em class="rfc2119"
                title="MUST">MUST</em> abort these steps.
          </li>
          <li>On receiving a valid 200 OK response, run the following steps:
            <ol class="rule">
              <li>Let <var>callback ID</var> equal the string value of the first included <em>SID</em> header, if it
              exists.
              </li>
              <li>Let <var>timeout date</var> equal the sum of the current UTC date value plus the integer value of the
              first included <em>TIMEOUT</em> header (minus the leading string of <code>Second-</code>), if it exists.
              </li>
              <li>Run the following steps asynchronously and continue to the step labeled <em>listen</em> below.
              </li>
              <li>
                <em>Refresh Subscription</em>: Run the following steps at a set interval (X) within the <a href=
                "#dfn-user-agent"
                    class="internalDFN">user agent</a>:
                <ol class="rule">
                  <li>Let <var>current date</var> equal the current UTC date.
                  </li>
                  <li>If <var>current date</var> is less than the <var>timeout date</var> then continue to the step
                  labeled <em>refresh subscription</em> above.
                  </li>
                  <li>Send a <abbr title="Hypertext Transfer Protocol">HTTP</abbr> SUBSCRIBE request with a
                  <em>SID</em> header with the string value of <var>callback ID</var> and a user-agent defined
                  <em>TIMEOUT</em> header (in the form <code>Second-XX</code> where <code>XX</code> is the user-agent
                  defined timeout value in seconds) towards the <var>network service record</var>'s
                  <code>eventsUrl</code> property.
                  </li>
                  <li>On receiving a valid 200 OK, update <var>callback ID</var> with the string value of the first
                  included <em>SID</em> header and set <var>timeout date</var> to the sum of the current UTC date value
                  plus the integer value of the first included <em>TIMEOUT</em> header (minus the leading string of
                  <code>Second-</code>), if it exists. If the current date is greater than or equal to <var>timeout
                  date</var> then the <a href="#dfn-user-agent"
                        class="internalDFN">user agent</a> <em class="rfc2119"
                        title="SHOULD">SHOULD</em> continue from the step labeled <em>refresh subscription</em> above.
                        For all non 200 OK responses the <a href="#dfn-user-agent"
                        class="internalDFN">user agent</a> <em class="rfc2119"
                        title="SHOULD">SHOULD</em> continue from the step labeled <em>refresh subscription</em> above.
                  </li>
                </ol>
              </li>
              <li>
                <em>Listen</em>: For each <abbr title="Hypertext Transfer Protocol">HTTP</abbr> NOTIFY request received
                at the <var>callback URL</var> the <a href="#dfn-user-agent"
                    class="internalDFN">user agent</a> is to run the following steps:
                <ol class="rule">
                  <li>Let <var>content clone</var> be the result of obtaining the message body of the <abbr title=
                  "Hypertext Transfer Protocol">HTTP</abbr> NOTIFY request. If <var>content clone</var> is empty, then
                  the <a href="#dfn-user-agent"
                        class="internalDFN">user agent</a> <em class="rfc2119"
                        title="MUST">MUST</em> abort these steps.
                  </li>
                  <li>Let <var>notification event</var> be a new simple event that uses the <a href=
                  "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
                        class="externalDFN"><code>Event</code></a> interface with the name <a href=
                        "#event-notify"><code>notify</code></a>, which does not bubble, is not cancellable, and has no
                        default action.
                  </li>
                  <li>Let the <code>data</code> attribute of <var>notification event</var> have the DOMString value of
                  <var>content clone</var>.
                  </li>
                  <li>
                    <a href="http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
                        class="externalDFN">Queue a task</a> to dispatch <var>notification event</var> at the current
                        <a href="#networkservice"
                        class="internalDFN"><code>NetworkService</code></a> object.
                  </li>
                  <li>Return a <abbr title="Hypertext Transfer Protocol">HTTP</abbr> 200 OK response to the sender of
                  the <abbr title="Hypertext Transfer Protocol">HTTP</abbr> NOTIFY request.
                  </li>
                </ol>
              </li>
            </ol>
          </li>
        </ol>
        <p>
          A <a href="#dfn-user-agent"
             class="internalDFN">user agent</a> can <dfn id=
             "dfn-terminate-an-existing-upnp-events-subscription">terminate an existing UPnP Events Subscription</dfn>
             at any time for a <var>network service record</var> by sending an <abbr title=
             "Hypertext Transfer Protocol">HTTP</abbr> UNSUBSCRIBE request - as defined in 'Section 4.1.4: Cancelling a
             subscription with UNSUBSCRIBE' in [<cite><a class="bibref"
             href="#bib-UPNP-DEVICEARCH11">UPNP-DEVICEARCH11</a></cite>] - with a HOST header set to that <var>active
             service</var>'s <code>eventsUrl</code> property and a SID header set to the <var>callback ID</var>
             obtained when the initial <a href="#dfn-setup-a-upnp-events-subscription"
             class="internalDFN">setup a UPnP Events Subscription</a> action occurred.
        </p>
      </section>
      <section id="discovery-and-launch-protocol-dial">
        <h3 aria-level="2"
            role="heading"
            id="h3_discovery-and-launch-protocol-dial">
          <span class="secno">8.3</span> Discovery and Launch Protocol (<abbr title=
          "Discovery and Launch Protocol">DIAL</abbr>)
        </h3>
        <p>
          A user agent that implements <abbr title="Discovery and Launch Protocol">DIAL</abbr> service discovery
          <em class="rfc2119"
             title="MUST">MUST</em> issue a <dfn id="dfn-search-request-for-dial-enabled-devices">search request for
             <abbr title="Discovery and Launch Protocol">DIAL</abbr>-enabled devices</dfn> against the user's current
             local network according to the full normative text and timing provided in 'Section 1.3.2: Search request
             with M-SEARCH' detailed in [<cite><a class="bibref"
             href="#bib-UPNP-DEVICEARCH11">UPNP-DEVICEARCH11</a></cite>].
        </p>
        <p>
          Let <var>dial version</var> be the version number specified in the <a href="#dfn-valid-service-type"
             class="internalDFN">valid service type</a> token. Let <var>dial search target</var> be the concatentation
             of the <code>urn:dial-multiscreen-org:service:dial:</code> string constant with the <var>dial
             version</var> (currently, <var>dial version</var> can only be <code>1</code>)
        </p>
        <p>
          The user agent <em class="rfc2119"
             title="MUST">MUST</em> issue all <a title="search request for DIAL-enabled devices"
             href="#dfn-search-request-for-dial-enabled-devices"
             class="internalDFN">search requests for <abbr title="Discovery and Launch Protocol">DIAL</abbr>-enabled
             devices</a> with a <abbr title="Hypertext Transfer Protocol">HTTP</abbr> request line equal to
             <code>M-SEARCH * <abbr title="Hypertext Transfer Protocol">HTTP</abbr>/1.1</code>, with a HOST header
             equal to the reserved multicast address and port of <code>239.255.255.250:1900</code>, a MAN header equal
             to <code>ssdp:discover</code>, an ST header equal to <var>dial search target</var> and a user-agent
             defined MX header equal to a <dfn id="dfn-maximum-dial-advertisement-response-wait-time">maximum
             <abbr title="Discovery and Launch Protocol">DIAL</abbr> advertisement response wait time</dfn> value
             between <code>1</code> and <code>5</code> seconds.
        </p>
        <p>
          The user agent <em class="rfc2119"
             title="MUST">MUST</em> listen for any incoming responses to a <a href=
             "#dfn-search-request-for-dial-enabled-devices"
             class="internalDFN">search request for <abbr title="Discovery and Launch Protocol">DIAL</abbr>-enabled
             devices</a>.
        </p>
        <p>
          For each <abbr title="Hypertext Transfer Protocol">HTTP</abbr> Response following an initial <a href=
          "#dfn-search-request-for-dial-enabled-devices"
             class="internalDFN">search request for <abbr title="Discovery and Launch Protocol">DIAL</abbr>-enabled
             devices</a> sent on a <a href="#dfn-standard-upnp-address-and-port"
             class="internalDFN">standard UPnP address and port</a> the user agent <em class="rfc2119"
             title="MUST">MUST</em> run the following steps:
        </p>
        <ol class="rule">
          <li>If the <abbr title="Hypertext Transfer Protocol">HTTP</abbr> Response is not a <abbr title=
          "Hypertext Transfer Protocol">HTTP</abbr> 200 OK response then this response is invalid and the user agent
          <em class="rfc2119"
                title="MUST">MUST</em> discard this response, abort any remaining steps and return. The user agent
                <em class="rfc2119"
                title="MAY">MAY</em> issue a new <a href="#dfn-search-request-for-dial-enabled-devices"
                class="internalDFN">search request for <abbr title="Discovery and Launch Protocol">DIAL</abbr>-enabled
                devices</a> as a result of this error occurring.
          </li>
          <li>If the <a href="#dfn-maximum-dial-advertisement-response-wait-time"
                class="internalDFN">maximum <abbr title="Discovery and Launch Protocol">DIAL</abbr> advertisement
                response wait time</a> has been exceeded since the initial <a href=
                "#dfn-search-request-for-dial-enabled-devices"
                class="internalDFN">search request for <abbr title="Discovery and Launch Protocol">DIAL</abbr>-enabled
                devices</a> was sent then the <a href="#dfn-http-response"
                class="internalDFN"><abbr title="Hypertext Transfer Protocol">HTTP</abbr> Response</a> is invalid and
                the user agent <em class="rfc2119"
                title="MUST">MUST</em> discard this response, abort any remaining steps and return. The user agent
                <em class="rfc2119"
                title="MAY">MAY</em> stop listening for responses from the current <a href=
                "#dfn-search-request-for-dial-enabled-devices"
                class="internalDFN">search request for <abbr title="Discovery and Launch Protocol">DIAL</abbr>-enabled
                devices</a> as a result of this error occurring. Equally, the user agent <em class="rfc2119"
                title="MAY">MAY</em> issue a new <a href="#dfn-search-request-for-dial-enabled-devices"
                class="internalDFN">search request for <abbr title="Discovery and Launch Protocol">DIAL</abbr>-enabled
                devices</a> as a result of this error occurring.
          </li>
          <li>Let <var>dial device</var> be an Object with a property for each <abbr title=
          "Hypertext Transfer Protocol">HTTP</abbr> header received in the <a href="#dfn-http-response"
                class="internalDFN"><abbr title="Hypertext Transfer Protocol">HTTP</abbr> Response</a>, with each key
                being the name of a <abbr title="Hypertext Transfer Protocol">HTTP</abbr> response header and each
                value being that <abbr title="Hypertext Transfer Protocol">HTTP</abbr> response header's value.
          </li>
          <li>If <var>dial device</var> does not contain at least one <var>CACHE-CONTROL</var> entry, at least one
          <var>USN</var> entry, at least one <var>ST</var> entry and at least one <var>LOCATION</var> entry or the
          value of its <var>ST</var> entry is not <var>dial search target</var>, then the <a href="#dfn-http-response"
                class="internalDFN"><abbr title="Hypertext Transfer Protocol">HTTP</abbr> Response</a> is invalid and
                the <a href="#dfn-user-agent"
                class="internalDFN">user agent</a> <em class="rfc2119"
                title="MUST">MUST</em> discard this response, abort any remaining steps and return.
          </li>
          <li>The user agent <em class="rfc2119"
                title="MUST">MUST</em> run the rule for <a href="#dfn-obtaining-a-upnp-device-description-file"
                class="internalDFN">obtaining a UPnP Device Description File</a> passing in the first occurrence of
                <var>LOCATION</var> from <var>dial device</var> as the <var>device descriptor URL</var> argument and
                the first occurrence of <var>USN</var> from <var>dial device</var> as the <var>device identifier</var>
                argument and the first occurrence of <var>CACHE-CONTROL</var> from <var>dial device</var> (minus the
                leading string of <code>max-age=</code>) as the <var>device expiry</var> argument.
          </li>
        </ol>
        <p>
          The rule for <dfn id="dfn-obtaining-a-dial-device-description-file">obtaining a <abbr title=
          "Discovery and Launch Protocol">DIAL</abbr> Device Description File</dfn> is the process of obtaining the
          contents of a standard UPnP Device Description [<cite><a class="bibref"
             href="#bib-UPNP-DEVICEARCH11">UPNP-DEVICEARCH11</a></cite>] from a URL-based resource. This rule takes
             three arguments - <var>device descriptor URL</var>, <var>device identifier</var> and <var>device
             expiry</var> - and when called the user agent <em class="rfc2119"
             title="MUST">MUST</em> run the following steps:
        </p>
        <ol class="rule">
          <li>Let <var>device descriptor file</var> contain the contents of the file located at the URL provided in
          <var>device descriptor URL</var> obtained according to the rules defined in 'Section 2.11: Retrieving a
          description using <abbr title="Hypertext Transfer Protocol">HTTP</abbr>' in [<cite><a class="bibref"
               href="#bib-UPNP-DEVICEARCH11">UPNP-DEVICEARCH11</a></cite>].
          </li>
          <li>Let <var>application url</var> be the value of the first occurrence of the <code>Application-URL</code>
          response header field obtained according to the rules defined in 'Section 5.4: Device Description Response'
          in [<a href="https://sites.google.com/a/dial-multiscreen.org/dial/dial-protocol-specification"><abbr title=
          "Discovery and Launch Protocol">DIAL</abbr></a>]
          </li>
          <li>If the value provided in <var>device descriptor URL</var> cannot be resolved as a reachable URL on the
          current network or the <var>device descriptor file</var> remains empty or <var>application url</var> is
          undefined then it is invalid and the <a href="#dfn-user-agent"
                class="internalDFN">user agent</a> <em class="rfc2119"
                title="MUST">MUST</em> abort any remaining steps and return.
          </li>
          <li>Run the following steps to add the newly discovered <abbr title=
          "Discovery and Launch Protocol">DIAL</abbr> service:
            <ol class="rule">
              <li>Let <var>network service record</var> be a new Object consisting of the following empty properties:
              <code>id</code>, <code>deviceId</code>, <code>name</code>, <code>type</code>, <code>url</code>,
              <code>expiryTimestamp</code>.
              </li>
              <li>Set <var>network service record</var>'s <code>id</code> property to the first occurrence of the
              <code>&lt;UDN&gt;</code> element in the <var>descriptor file</var> prefixed with the <code>dial:</code>
              string constant
              </li>
              <li>Set <var>network service record</var>'s <code>deviceId</code> property to the value of <var>device
              identifier</var>.
              </li>
              <li>Set <var>network service record</var>'s <code>name</code> property to the string value of the first
              occurrence of the <code>&lt;friendlyName&gt;</code> element in the <var>descriptor file</var>.
              </li>
              <li>Set <var>network service record</var>'s <code>type</code> property to <var>dial search target</var>.
              </li>
              <li>Set <var>network service record</var>'s <code>url</code> property to the string value of the
              <var>application url</var>.
              </li>
              <li>Set <var>network service record</var>'s <code>expiryTimestamp</code> property to the value of the
              current date, in UTC timestamp format, plus the value of <var>device expiry</var>.
              </li>
              <li>Run the general rule for <a href="#dfn-adding-an-available-service"
                    class="internalDFN">adding an available service</a>, passing in the current <var>network service
                    record</var> as the only argument.
              </li>
            </ol>
          </li>
        </ol>
      </section>
      <section id="network-topology-monitoring">
        <h3 aria-level="2"
            role="heading"
            id="h3_network-topology-monitoring">
          <span class="secno">8.4</span> Network Topology Monitoring
        </h3>
        <div>
          <p>
            When the <a href="#dfn-user-agent"
               class="internalDFN">user agent</a> detects that the user has dropped from a connected network then, for
               each <var>existing service record</var> in the <a href="#dfn-list-of-available-service-records"
               class="internalDFN">list of available service records</a> discovered via that network connection, the
               <a href="#dfn-user-agent"
               class="internalDFN">user agent</a> <em class="rfc2119"
               title="MUST">MUST</em> run the general rule for <a href="#dfn-removing-an-available-service"
               class="internalDFN">removing an available service</a> passing in each <var>existing service
               record</var>'s <code>id</code> property as the only argument for each call.
          </p>
          <p>
            When the <a href="#dfn-user-agent"
               class="internalDFN">user agent</a> detects that the user has connected to a new network or reconnected
               to an existing network, then it <em class="rfc2119"
               title="SHOULD">SHOULD</em> restart its discovery mechanisms as defined in the <a href=
               "#service-discovery">Service Discovery</a> section of this specification, maintaining the existing
               <a href="#dfn-list-of-active-service-managers"
               class="internalDFN">list of active service managers</a> currently in use.
          </p>
        </div>
      </section>
    </section>
    <section id="events-summary">
      <h2 aria-level="1"
          role="heading"
          id="h2_events-summary">
        <span class="secno">9.</span> Events Summary
      </h2>
      <p>
        The following events are dispatched on the <a href="#networkservices"><code>NetworkServices</code></a> and/or
        <a href="#networkservice"><code>NetworkService</code></a> objects:
      </p>
      <table border="1">
        <thead>
          <tr>
            <th>
              <span>Event name</span>
            </th>
            <th>
              <span>Interface</span>
            </th>
            <th>
              <span>Dispatched when...</span>
            </th>
          </tr>
        </thead>
        <tbody>
          <tr>
            <td>
              <dfn id="event-servicefound"><code>servicefound</code></dfn>
            </td>
            <td>
              <a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
                  class="externalDFN"><code>Event</code></a>
            </td>
            <td>
              When a <a href="#dfn-new-service"
                  class="internalDFN">new service</a> that matches one of the <a title="valid service type"
                  href="#dfn-valid-service-type"
                  class="internalDFN">requested type tokens</a> is found in the current network.
            </td>
          </tr>
          <tr>
            <td>
              <dfn id="event-servicelost"><code>servicelost</code></dfn>
            </td>
            <td>
              <a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
                  class="externalDFN"><code>Event</code></a>
            </td>
            <td>
              When an <a href="#dfn-existing-service"
                  class="internalDFN">existing service</a> that matches one of the <a title="valid service type"
                  href="#dfn-valid-service-type"
                  class="internalDFN">requested type tokens</a> gracefully leaves or expires from the current network.
            </td>
          </tr>
          <tr>
            <td>
              <dfn id="event-available"><code>available</code></dfn>
            </td>
            <td>
              <a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
                  class="externalDFN"><code>Event</code></a>
            </td>
            <td>
              When a <a href="#dfn-current-service"
                  class="internalDFN">current service</a> renews its service registration within the current network.
            </td>
          </tr>
          <tr>
            <td>
              <dfn id="event-unavailable"><code>unavailable</code></dfn>
            </td>
            <td>
              <a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
                  class="externalDFN"><code>Event</code></a>
            </td>
            <td>
              When a <a href="#dfn-current-service"
                  class="internalDFN">current service</a> gracefully leaves or otherwise expires from the current
                  network.
            </td>
          </tr>
          <tr>
            <td>
              <dfn id="event-notify"><code>notify</code></dfn>
            </td>
            <td>
              <a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
                  class="externalDFN"><code>Event</code></a>
            </td>
            <td>
              When a valid UPnP Events Subscription Message is received on a <a href=
              "#dfn-user-agent-generated-callback-url"
                  class="internalDFN">user-agent generated callback url</a> for a <a href="#dfn-current-service"
                  class="internalDFN">current service</a>. This event never fires for Zeroconf-based services.
            </td>
          </tr>
        </tbody>
      </table>
    </section>
    <section id="garbage-collection">
      <h2 aria-level="1"
          role="heading"
          id="h2_garbage-collection">
        <span class="secno">10.</span> Garbage collection
      </h2>
      <p>
        There is an <dfn id="dfn-implied-strong-reference">implied strong reference</dfn> from any IDL attribute in
        this <abbr title="Application Programming Interface">API</abbr> that returns a pre-existing object to that
        object.
      </p>
      <div class="note">
        <div class="note-title"
             aria-level="2"
             role="heading"
             id="h_note_3">
          <span>Note</span>
        </div>
        <p class="">
          For example, if a <a href="#networkservices"
             class="internalDFN"><code>NetworkServices</code></a> object has one or more <a href=
             "#dfn-indexed-properties"
             class="internalDFN">indexed properties</a> attached to it then there is a strong reference from that
             <a href="#networkservices"
             class="internalDFN"><code>NetworkServices</code></a> object toward each of its <a href=
             "#dfn-indexed-properties"
             class="internalDFN">indexed properties</a>.
        </p>
      </div>
      <p>
        If a <a href="#dfn-user-agent"
           class="internalDFN">user agent</a> is to <dfn id="dfn-make-disappear">make disappear</dfn> a <a href=
           "#networkservices"
           class="internalDFN"><code>NetworkServices</code></a> object (this happens when a <a href=
           "http://www.whatwg.org/specs/web-apps/current-work/multipage/dom.html#document"
           class="externalDFN"><code>Document</code></a> object goes away), the <a href="#dfn-user-agent"
           class="internalDFN">user agent</a> <em class="rfc2119"
           title="MUST">MUST</em> remove this object from the <a href="#dfn-list-of-active-service-managers"
           class="internalDFN">list of active service managers</a>.
      </p>
    </section>
    <section id="use-cases-and-requirements">
      <h2 aria-level="1"
          role="heading"
          id="h2_use-cases-and-requirements">
        <span class="secno">11.</span> Use Cases and Requirements
      </h2>
      <p>
        This section covers what the requirements are for this <abbr title=
        "Application Programming Interface">API</abbr>, as well as illustrates some use cases.
      </p>
      <ul class="rule">
        <li>Once a user has given permission, user agents should provide the ability for Web pages to communicate
        directly with a Local-networked Service.
          <ul class="rule">
            <li>Example: A web-based TV remote control. A Web page wants to control the current user's TV, changing the
            programming shown or increasing/decreasing/muting the volume of the Local-networked Device. The Web page
            requests a service type that is known to be implemented by television sets to which it has the application
            logic to communicate. Local devices providing the request service types are discovered and presented to the
            user for authorization. The user selects one or more of the discovered television sets to be accessible to
            the current Web page and then clicks 'Share'. The Web page can now communicate directly with the
            user-authorized Local-networked services.
            </li>
          </ul>
        </li>
        <li>Web pages should be able to communicate with Local-networked Services using the messaging channel supported
        by those Devices.
          <ul class="rule">
            <li>Example: A Web page advertises that it is capable of controlling multiple Home Media Servers. The user
            can select their Home Media Server type from a drop-down list, at which point the Web page sends a request
            to the user agent to connect with the associated service type of the Home Media Server. The Media Server
            selected implements a Web Socket channel for bi-directional service communication and so the Web page opens
            a web socket to the requested Media Server and can communicate as required via that appropriate channel.
            </li>
          </ul>
        </li>
        <li>Web pages should be able to communicate with Local-networked Services using the messaging format supported
        by those Devices.
          <ul class="rule">
            <li>Example: A Web page advertises that it is capable of interacting with and controlling multiple types of
            Home Media Server. The user can select their Home Media Server type from a drop-down list or known Media
            Servers, at which point the Web page sends a request to the user agent to connect with the associated
            service type (and, optionally, the associated event type) of the Home Media Server. The communication
            protocols supported by Home Media Servers typically vary between UPnP, JSON-RPC, Protocol Buffers or other
            messaging formats depending on the Home Media Server requested. The Web page is able to communicate with
            the user-selected Home Media Server in the messaging format supported by that Device, which, in this
            example is a simple key/value pair text format.
            </li>
          </ul>
        </li>
        <li>Web pages should not be able to communicate with Local-networked Services that have not been authorized by
        the user thereby maintaining the user's privacy.
          <ul class="rule">
            <li>Example: A Web page requests access to one type of Local-networked service. The user authorizes access
            to that particular service. Other services running on that same device, and on other devices within the
            network, should not be accessible to the current Web page.
            </li>
          </ul>
        </li>
        <li>A user should be able to share one or more Local-networked Services based on a particular service type
        request from a Web page.
          <ul class="rule">
            <li>Example: A Web page is capable of interacting with a specific profile of Local-networked Service. As
            such, it makes a request to the user agent to access those services, of which multiple matches are found.
            The user is capable of selecting one or more of the discovered services to share with the Web page. The Web
            page can then implement a drag-and-drop interface for the user to drag specific actions on to one or more
            of the authorized Local-networked Services.
            </li>
          </ul>
        </li>
        <li>User agents should provide an <abbr title="Application Programming Interface">API</abbr> exposed to script
        that exposes the features above. The user is notified by UI anytime interaction with Local-networked Services
        is requested, giving the user full ability to cancel or abort the transaction. The user selects the
        Local-networked Services to be connected to the current Web page, and can cancel these at any time. No
        invocations to these APIs occur silently without user intervention.
        </li>
      </ul>
    </section>
    <section class="informative appendix"
             id="examples">
      <h2 aria-level="1"
          role="heading"
          id="h2_examples">
        <span class="secno">A.</span> Examples
      </h2>
      <p>
        <em>This section is non-normative.</em>
      </p>
      <div class="example">
        <p>
          This sample code exposes a button. When clicked, this button is disabled and the user is prompted to offer a
          network service. The user may also select multiple network services. When the user has authorized a network
          service to be connected to the web page then the web page issues a simple command to get a list of all the
          albums stored on the connected media player service.
        </p>
        <p>
          The button is re-enabled only when the connected network service disconnects for whatever reason (the service
          becomes unavailable on the network, the user disconnects from their current network or the user revokes
          access to the service from the current web page). At this point the user can re-click the button to select a
          new network service to connect to the web page and the above steps are repeated.
        </p>
        <p>
          The provided service type identifier and service interaction used in this example is based on the
          well-defined service type and messaging format supported by the <a href="http://xbmc.org/about/">XBMC Media
          Server</a>.
        </p>
        <hr>
        <pre class="highlight prettyprint">
<span class="tag">&lt;input</span><span class="pln"> </span><span class="atn">type</span><span class=
"pun">=</span><span class="atv">"button"</span><span class="pln"> </span><span class="atn">value</span><span class=
"pun">=</span><span class="atv">"Start"</span><span class="pln"> </span><span class="atn">onclick</span><span class=
"pun">=</span><span class="atv">"</span><span class="pln">start</span><span class="pun">()</span><span class=
"atv">"</span><span class="pln"> </span><span class="atn">id</span><span class="pun">=</span><span class=
"atv">"startBtn"</span><span class="tag">/&gt;</span><span class="pln">
</span><span class="tag">&lt;div</span><span class="pln"> </span><span class="atn">id</span><span class=
"pun">=</span><span class="atv">"debugconsole"</span><span class="tag">&gt;&lt;/div&gt;</span><span class="pln">

</span><span class="tag">&lt;script&gt;</span><span class="pln">
 </span><span class="kwd">var</span><span class="pln"> startBtn </span><span class="pun">=</span><span class=
"pln"> document</span><span class="pun">.</span><span class="pln">getElementById</span><span class=
"pun">(</span><span class="str">'startBtn'</span><span class="pun">),</span><span class="pln">
     debug </span><span class="pun">=</span><span class="pln"> document</span><span class="pun">.</span><span class=
"pln">getElementById</span><span class="pun">(</span><span class="str">'debugconsole'</span><span class=
"pun">);</span><span class="pln">

 </span><span class="kwd">function</span><span class="pln"> start</span><span class="pun">()</span><span class=
"pln"> </span><span class="pun">{</span><span class="pln">
   </span><span class="kwd">if</span><span class="pun">(</span><span class="pln">navigator</span><span class=
"pun">.</span><span class="pln">getNetworkServices</span><span class="pun">)</span><span class=
"pln"> </span><span class="pun">{</span><span class="pln">
      navigator</span><span class="pun">.</span><span class="pln">getNetworkServices</span><span class=
"pun">(</span><span class="str">'zeroconf:_xbmc-jsonrpc._tcp'</span><span class="pun">).</span><span class=
"pln">then</span><span class="pun">(</span><span class="pln">gotXBMCService</span><span class=
"pun">).</span><span class="kwd">catch</span><span class="pun">(</span><span class="pln">error</span><span class=
"pun">);</span><span class="pln">
      startBtn</span><span class="pun">.</span><span class="pln">disabled </span><span class="pun">=</span><span class=
"pln"> </span><span class="kwd">true</span><span class="pun">;</span><span class="pln">
   </span><span class="pun">}</span><span class="pln"> </span><span class="kwd">else</span><span class=
"pln"> </span><span class="pun">{</span><span class="pln">
      debug</span><span class="pun">.</span><span class="pln">innerHTML </span><span class="pun">+=</span><span class=
"pln"> </span><span class="str">"&lt;br&gt;Service Discovery not supported!"</span><span class=
"pun">;</span><span class="pln">
   </span><span class="pun">}</span><span class="pln">
 </span><span class="pun">}</span><span class="pln">

 </span><span class="kwd">function</span><span class="pln"> gotXBMCService</span><span class="pun">(</span><span class=
"pln">services</span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">

</span><span class="com">// Listen for service disconnect messages</span><span class="pln">

   services</span><span class="pun">[</span><span class="lit">0</span><span class="pun">].</span><span class=
"pln">addEventListener</span><span class="pun">(</span><span class="str">'unavailable'</span><span class=
"pun">,</span><span class="pln"> </span><span class="kwd">function</span><span class="pln"> </span><span class=
"pun">(</span><span class="pln"> e </span><span class="pun">)</span><span class="pln"> </span><span class=
"pun">{</span><span class="pln">
       debug</span><span class="pun">.</span><span class="pln">innerHTML </span><span class="pun">+=</span><span class=
"pln"> </span><span class="str">"&lt;br&gt;"</span><span class="pln"> </span><span class="pun">+</span><span class=
"pln"> services</span><span class="pun">[</span><span class="lit">0</span><span class="pun">].</span><span class=
"pln">name </span><span class="pun">+</span><span class="pln"> </span><span class=
"str">" disconnected."</span><span class="pun">;</span><span class="pln">
       startBtn</span><span class="pun">.</span><span class="pln">disabled </span><span class=
"pun">=</span><span class="pln"> </span><span class="kwd">false</span><span class="pun">;</span><span class="pln">
   </span><span class="pun">},</span><span class="pln"> </span><span class="kwd">false</span><span class=
"pun">);</span><span class="pln">

</span><span class=
"com">// Send a service message to get albums list (and process the service response)</span><span class="pln">

   </span><span class="kwd">var</span><span class="pln"> svcXhr </span><span class="pun">=</span><span class=
"pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">XMLHttpRequest</span><span class=
"pun">();</span><span class="pln">
   svcXhr</span><span class="pun">.</span><span class="pln">open</span><span class="pun">(</span><span class=
"str">"POST"</span><span class="pun">,</span><span class="pln"> services</span><span class="pun">[</span><span class=
"lit">0</span><span class="pun">].</span><span class="pln">url </span><span class="pun">+</span><span class=
"pln"> </span><span class="str">"/getAlbums"</span><span class="pun">);</span><span class="pln"> </span><span class=
"com">// services[0].url and its sub-resources are</span><span class="pln">
                                                        </span><span class=
"com">// available for cross-site XHR use.</span><span class="pln">

   svcXhr</span><span class="pun">.</span><span class="pln">setRequestHeader</span><span class=
"pun">(</span><span class="str">'Content-Type'</span><span class="pun">,</span><span class="pln"> </span><span class=
"str">'application/json-rpc'</span><span class="pun">);</span><span class="pln">

   svcXhr</span><span class="pun">.</span><span class="pln">addEventListener</span><span class=
"pun">(</span><span class="str">'readystatechange'</span><span class="pun">,</span><span class=
"pln"> </span><span class="kwd">function</span><span class="pln"> </span><span class="pun">(</span><span class=
"pln"> response </span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
     </span><span class="kwd">if</span><span class="pun">(</span><span class="pln"> response</span><span class=
"pun">.</span><span class="pln">readyState </span><span class="pun">!=</span><span class="pln"> </span><span class=
"lit">4</span><span class="pln"> </span><span class="pun">||</span><span class="pln"> response</span><span class=
"pun">.</span><span class="pln">status </span><span class="pun">!=</span><span class="pln"> </span><span class=
"lit">200</span><span class="pln"> </span><span class="pun">)</span><span class="pln">
        </span><span class="kwd">return</span><span class="pun">;</span><span class="pln">
     debug</span><span class="pun">.</span><span class="pln">innerHTML </span><span class="pun">+=</span><span class=
"pln"> </span><span class="str">"&lt;br&gt;"</span><span class="pln"> </span><span class="pun">+</span><span class=
"pln"> services</span><span class="pun">[</span><span class="lit">0</span><span class="pun">].</span><span class=
"pln">name </span><span class="pun">+</span><span class="pln"> </span><span class=
"str">" response received: "</span><span class="pun">;</span><span class="pln">
     debug</span><span class="pun">.</span><span class="pln">textContent </span><span class="pun">+=</span><span class=
"pln"> JSON</span><span class="pun">.</span><span class="pln">parse</span><span class="pun">(</span><span class=
"pln">response</span><span class="pun">.</span><span class="pln">responseText</span><span class=
"pun">);</span><span class="pln">
   </span><span class="pun">},</span><span class="pln"> </span><span class="kwd">false</span><span class=
"pun">);</span><span class="pln">

   </span><span class="kwd">var</span><span class="pln"> svcMsg </span><span class="pun">=</span><span class=
"pln"> </span><span class="pun">[</span><span class="pln">
     </span><span class="pun">{</span><span class="pln"> </span><span class="str">"jsonrpc"</span><span class=
"pun">:</span><span class="pln"> </span><span class="str">"2.0"</span><span class="pun">,</span><span class=
"pln"> </span><span class="str">"method"</span><span class="pun">:</span><span class="pln"> </span><span class=
"str">"AudioLibrary.GetAlbums"</span><span class="pun">,</span><span class="pln"> </span><span class=
"str">"params"</span><span class="pun">:</span><span class="pln"> </span><span class="pun">{</span><span class=
"pln"> </span><span class="str">"genreid"</span><span class="pun">:</span><span class="pln"> </span><span class=
"pun">-</span><span class="lit">1</span><span class="pun">,</span><span class="pln">
         </span><span class="str">"artistid"</span><span class="pun">:</span><span class="pln"> </span><span class=
"pun">-</span><span class="lit">1</span><span class="pun">,</span><span class="pln"> </span><span class=
"str">"start"</span><span class="pun">:</span><span class="pln"> </span><span class="pun">-</span><span class=
"lit">1</span><span class="pun">,</span><span class="pln"> </span><span class="str">"end"</span><span class=
"pun">:</span><span class="pln"> </span><span class="pun">-</span><span class="lit">1</span><span class=
"pln"> </span><span class="pun">},</span><span class="pln"> </span><span class="str">"id"</span><span class=
"pun">:</span><span class="pln"> </span><span class="str">"1"</span><span class="pln"> </span><span class=
"pun">}</span><span class="pln">
   </span><span class="pun">];</span><span class="pln">

   svcXhr</span><span class="pun">.</span><span class="pln">send</span><span class="pun">(</span><span class=
"pln">JSON</span><span class="pun">.</span><span class="pln">stringify</span><span class="pun">(</span><span class=
"pln">svcMsg</span><span class="pun">));</span><span class="pln">
   debug</span><span class="pun">.</span><span class="pln">innerHTML </span><span class="pun">+=</span><span class=
"pln"> </span><span class="str">"&lt;br&gt;"</span><span class="pln"> </span><span class="pun">+</span><span class=
"pln"> services</span><span class="pun">[</span><span class="lit">0</span><span class="pun">].</span><span class=
"pln">name </span><span class="pun">+</span><span class="pln"> </span><span class=
"str">" request sent: "</span><span class="pun">;</span><span class="pln">
   debug</span><span class="pun">.</span><span class="pln">textContent </span><span class="pun">+=</span><span class=
"pln"> JSON</span><span class="pun">.</span><span class="pln">stringify</span><span class="pun">(</span><span class=
"pln">svcMsg</span><span class="pun">);</span><span class="pln">

 </span><span class="pun">}</span><span class="pln">

 </span><span class="kwd">function</span><span class="pln"> error</span><span class="pun">(</span><span class=
"pln"> err </span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
   debug</span><span class="pun">.</span><span class="pln">innerHTML </span><span class="pun">+=</span><span class=
"pln"> </span><span class="str">"&lt;br&gt;An error occurred obtaining a local network service."</span><span class=
"pun">;</span><span class="pln">
   startBtn</span><span class="pun">.</span><span class="pln">disabled </span><span class="pun">=</span><span class=
"pln"> </span><span class="kwd">false</span><span class="pun">;</span><span class="pln">
 </span><span class="pun">}</span><span class="pln">
</span><span class="tag">&lt;/script&gt;</span>
</pre>
      </div>
      <div class="example">
        <p>
          This sample exposes a drop-down list containing a number of common Home-based audio devices. When the user
          selects an audio device from the list provided, they are prompted to authorize a network service based on the
          service type requested. The user may also select multiple network services matching the selected service
          type. In this example, the user selects their make as being <var>Sony</var> and their model as being
          <var>Bravia S1000</var> from which the Web page can derive a service type
          (<var>urn:schemas-upnp-org:service:RenderingControl:1</var>).<br>
          <br>
          Once the user has authorized the device, the web page sends a simple mute command according to the messaging
          format supported by the device.
        </p>
        <hr>
        <pre class="highlight prettyprint">
<span class="tag">&lt;select</span><span class="pln"> </span><span class="atn">name</span><span class=
"pun">=</span><span class="atv">"make"</span><span class="pln"> </span><span class="atn">id</span><span class=
"pun">=</span><span class="atv">"make"</span><span class="tag">&gt;</span><span class="pln">
  </span><span class="tag">&lt;option</span><span class="pln"> </span><span class="atn">selected</span><span class=
"pun">=</span><span class="atv">"selected"</span><span class="pln"> </span><span class=
"atn">disabled</span><span class="pun">=</span><span class="atv">"disabled"</span><span class=
"tag">&gt;</span><span class="pln">Select make</span><span class="tag">&lt;/option&gt;</span><span class="pln">
  </span><span class="tag">&lt;option&gt;</span><span class="pln">Sony</span><span class=
"tag">&lt;/option&gt;</span><span class="pln">
  </span><span class="tag">&lt;option&gt;</span><span class="pln">Philips</span><span class=
"tag">&lt;/option&gt;</span><span class="pln">
  </span><span class="tag">&lt;option&gt;</span><span class="pln">Alba</span><span class=
"tag">&lt;/option&gt;</span><span class="pln">
</span><span class="tag">&lt;/select&gt;</span><span class="pln">
</span><span class="tag">&lt;select</span><span class="pln"> </span><span class="atn">name</span><span class=
"pun">=</span><span class="atv">"model"</span><span class="pln"> </span><span class="atn">id</span><span class=
"pun">=</span><span class="atv">"model"</span><span class="tag">&gt;&lt;/select&gt;</span><span class="pln">
</span><span class="tag">&lt;div</span><span class="pln"> </span><span class="atn">id</span><span class=
"pun">=</span><span class="atv">"debugconsole"</span><span class="tag">&gt;&lt;/div&gt;</span><span class="pln">

</span><span class="tag">&lt;script&gt;</span><span class="pln">
  </span><span class="kwd">var</span><span class="pln"> debug </span><span class="pun">=</span><span class=
"pln"> document</span><span class="pun">.</span><span class="pln">getElementById</span><span class=
"pun">(</span><span class="str">'debugconsole'</span><span class="pun">);</span><span class="pln">

  </span><span class="kwd">var</span><span class="pln"> models </span><span class="pun">=</span><span class=
"pln"> </span><span class="pun">{</span><span class="pln">
    </span><span class="str">"Sony"</span><span class="pun">:</span><span class="pln"> </span><span class=
"pun">[</span><span class="pln">
      </span><span class="pun">{</span><span class="str">"name"</span><span class="pun">:</span><span class=
"pln"> </span><span class="str">"Bravia TV S1000"</span><span class="pun">,</span><span class=
"pln"> </span><span class="str">"type"</span><span class="pun">:</span><span class="pln"> </span><span class=
"str">"upnp"</span><span class="pun">,</span><span class="pln"> </span><span class="str">"service"</span><span class=
"pun">:</span><span class="pln"> </span><span class=
"str">"urn:schemas-upnp-org:service:RenderingControl:1"</span><span class="pln"> </span><span class=
"pun">},</span><span class="pln">
      </span><span class="pun">{</span><span class="str">"name"</span><span class="pun">:</span><span class=
"pln"> </span><span class="str">"Bravia TV S2000"</span><span class="pun">,</span><span class=
"pln"> </span><span class="str">"type"</span><span class="pun">:</span><span class="pln"> </span><span class=
"str">"zeroconf"</span><span class="pun">,</span><span class="pln"> </span><span class=
"str">"service"</span><span class="pun">:</span><span class="pln"> </span><span class=
"str">"_mediarenderer._http._tcp"</span><span class="pln"> </span><span class="pun">},</span><span class="pln">
      </span><span class="pun">{</span><span class="str">"name"</span><span class="pun">:</span><span class=
"pln"> </span><span class="str">"HiFi WD10"</span><span class="pun">,</span><span class="pln"> </span><span class=
"str">"type"</span><span class="pun">:</span><span class="pln"> </span><span class="str">"upnp"</span><span class=
"pun">,</span><span class="pln"> </span><span class="str">"service"</span><span class="pun">:</span><span class=
"pln"> </span><span class="str">"urn:schemas-upnp-org:service:RenderingControl:1"</span><span class=
"pln"> </span><span class="pun">}</span><span class="pln">
    </span><span class="pun">],</span><span class="pln">
    </span><span class="str">"Philips"</span><span class="pun">:</span><span class="pln"> </span><span class=
"pun">[</span><span class="pln"> </span><span class="com">/* ... */</span><span class="pln"> </span><span class=
"pun">],</span><span class="pln">
    </span><span class="str">"Alba"</span><span class="pun">:</span><span class="pln"> </span><span class=
"pun">[</span><span class="pln"> </span><span class="com">/* ... */</span><span class="pln"> </span><span class=
"pun">]</span><span class="pln">
  </span><span class="pun">};</span><span class="pln">

  </span><span class="kwd">var</span><span class="pln"> makeEl </span><span class="pun">=</span><span class=
"pln"> document</span><span class="pun">.</span><span class="pln">getElementById</span><span class=
"pun">(</span><span class="str">"make"</span><span class="pun">),</span><span class="pln">
      modelEl </span><span class="pun">=</span><span class="pln"> document</span><span class="pun">.</span><span class=
"pln">getElementById</span><span class="pun">(</span><span class="str">"model"</span><span class=
"pun">);</span><span class="pln">

  makeEl</span><span class="pun">.</span><span class="pln">addEventListener</span><span class=
"pun">(</span><span class="str">'change'</span><span class="pun">,</span><span class="pln"> </span><span class=
"kwd">function</span><span class="pun">()</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
    modelEl</span><span class="pun">.</span><span class="pln">innerHTML </span><span class="pun">=</span><span class=
"pln"> </span><span class="str">""</span><span class="pun">;</span><span class="pln"> </span><span class=
"com">// reset</span><span class="pln">
    </span><span class="kwd">var</span><span class="pln"> defaultOption </span><span class="pun">=</span><span class=
"pln"> document</span><span class="pun">.</span><span class="pln">createElement</span><span class=
"pun">(</span><span class="str">"option"</span><span class="pun">);</span><span class="pln">
    defaultOption</span><span class="pun">.</span><span class="pln">textContent </span><span class=
"pun">=</span><span class="pln"> </span><span class="str">"Select model"</span><span class="pun">;</span><span class=
"pln">
    defaultOption</span><span class="pun">.</span><span class="pln">setAttribute</span><span class=
"pun">(</span><span class="str">"disabled"</span><span class="pun">,</span><span class="pln"> </span><span class=
"str">"disabled"</span><span class="pun">);</span><span class="pln">
    defaultOption</span><span class="pun">.</span><span class="pln">setAttribute</span><span class=
"pun">(</span><span class="str">"selected"</span><span class="pun">,</span><span class="pln"> </span><span class=
"str">"selected"</span><span class="pun">);</span><span class="pln">
    modelEl</span><span class="pun">.</span><span class="pln">appendChild</span><span class="pun">(</span><span class=
"pln">defaultOption</span><span class="pun">);</span><span class="pln">
    </span><span class="kwd">for</span><span class="pun">(</span><span class="kwd">var</span><span class=
"pln"> i </span><span class="pun">=</span><span class="pln"> </span><span class="lit">0</span><span class=
"pun">,</span><span class="pln"> l </span><span class="pun">=</span><span class="pln"> models</span><span class=
"pun">[</span><span class="pln">makeEl</span><span class="pun">.</span><span class="pln">value</span><span class=
"pun">].</span><span class="pln">length</span><span class="pun">;</span><span class="pln"> i </span><span class=
"pun">&lt;</span><span class="pln"> l</span><span class="pun">;</span><span class="pln"> i</span><span class=
"pun">++)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
      </span><span class="kwd">var</span><span class="pln"> option </span><span class="pun">=</span><span class=
"pln"> document</span><span class="pun">.</span><span class="pln">createElement</span><span class=
"pun">(</span><span class="str">"option"</span><span class="pun">);</span><span class="pln">
      option</span><span class="pun">.</span><span class="pln">textContent </span><span class=
"pun">=</span><span class="pln"> models</span><span class="pun">[</span><span class="pln">makeEl</span><span class=
"pun">.</span><span class="pln">value</span><span class="pun">][</span><span class="pln">i</span><span class=
"pun">][</span><span class="str">"name"</span><span class="pun">];</span><span class="pln">
      option</span><span class="pun">.</span><span class="pln">setAttribute</span><span class=
"pun">(</span><span class="str">"value"</span><span class="pun">,</span><span class="pln"> models</span><span class=
"pun">[</span><span class="pln">makeEl</span><span class="pun">.</span><span class="pln">value</span><span class=
"pun">][</span><span class="pln">i</span><span class="pun">][</span><span class="str">"type"</span><span class=
"pun">]</span><span class="pln"> </span><span class="pun">+</span><span class="pln"> </span><span class=
"str">":"</span><span class="pln"> </span><span class="pun">+</span><span class="pln"> models</span><span class=
"pun">[</span><span class="pln">makeEl</span><span class="pun">.</span><span class="pln">value</span><span class=
"pun">][</span><span class="pln">i</span><span class="pun">][</span><span class="str">"service"</span><span class=
"pun">]);</span><span class="pln">
      modelEl</span><span class="pun">.</span><span class="pln">appendChild</span><span class=
"pun">(</span><span class="pln">option</span><span class="pun">);</span><span class="pln">
    </span><span class="pun">}</span><span class="pln">
  </span><span class="pun">},</span><span class="pln"> </span><span class="kwd">false</span><span class=
"pun">);</span><span class="pln">

  modelEl</span><span class="pun">.</span><span class="pln">addEventListener</span><span class=
"pun">(</span><span class="str">'change'</span><span class="pun">,</span><span class="pln"> </span><span class=
"kwd">function</span><span class="pun">()</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
    </span><span class="kwd">if</span><span class="pun">(</span><span class="pln">navigator</span><span class=
"pun">.</span><span class="pln">getNetworkServices </span><span class="pun">&amp;&amp;</span><span class="pln">
         modelEl</span><span class="pun">.</span><span class="pln">value </span><span class="pun">==</span><span class=
"pln"> </span><span class="str">"upnp:urn:schemas-upnp-org:service:RenderingControl:1"</span><span class=
"pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
      </span><span class="kwd">var</span><span class="pln"> servicesPromise </span><span class=
"pun">=</span><span class="pln"> navigator</span><span class="pun">.</span><span class=
"pln">getNetworkServices</span><span class="pun">(</span><span class="pln">modelEl</span><span class=
"pun">.</span><span class="pln">value</span><span class="pun">).</span><span class="pln">then</span><span class=
"pun">(</span><span class="pln">successCallback</span><span class="pun">,</span><span class=
"pln"> errorCallback</span><span class="pun">);</span><span class="pln">
    </span><span class="pun">}</span><span class="pln"> </span><span class="kwd">else</span><span class=
"pln"> </span><span class="kwd">if</span><span class="pln"> </span><span class="pun">(</span><span class=
"pln">modelEl</span><span class="pun">.</span><span class="pln">value </span><span class="pun">==</span><span class=
"pln"> </span><span class="str">"zeroconf:_mediarenderer._http._tcp"</span><span class="pun">)</span><span class=
"pln"> </span><span class="pun">{</span><span class="pln">
      debug</span><span class="pun">.</span><span class="pln">innerHTML </span><span class="pun">+=</span><span class=
"pln"> </span><span class="str">"&lt;br&gt;Service type is not implemented by this application."</span><span class=
"pun">;</span><span class="pln">
    </span><span class="pun">}</span><span class="pln"> </span><span class="kwd">else</span><span class=
"pln"> </span><span class="pun">{</span><span class="pln">
      debug</span><span class="pun">.</span><span class="pln">innerHTML </span><span class="pun">+=</span><span class=
"pln"> </span><span class="str">"&lt;br&gt;Service Discovery is not supported!"</span><span class=
"pun">;</span><span class="pln">
    </span><span class="pun">}</span><span class="pln">
  </span><span class="pun">},</span><span class="pln"> </span><span class="kwd">false</span><span class=
"pun">);</span><span class="pln">
</span><span class="tag">&lt;/script&gt;</span><span class="pln">

</span><span class="tag">&lt;script&gt;</span><span class="pln">
  </span><span class="kwd">function</span><span class="pln"> successCallback</span><span class=
"pun">(</span><span class="pln"> services </span><span class="pun">)</span><span class="pln"> </span><span class=
"pun">{</span><span class="pln">

  </span><span class="com">// Listen for service push notification messages</span><span class="pln">

    services</span><span class="pun">[</span><span class="lit">0</span><span class="pun">].</span><span class=
"pln">addEventListener</span><span class="pun">(</span><span class="str">'notify'</span><span class=
"pun">,</span><span class="pln"> </span><span class="kwd">function</span><span class="pln"> </span><span class=
"pun">(</span><span class="pln"> msg </span><span class="pun">)</span><span class="pln"> </span><span class=
"pun">{</span><span class="pln">
         debug</span><span class="pun">.</span><span class="pln">innerHTML </span><span class=
"pun">+=</span><span class="pln"> </span><span class="str">"&lt;br&gt;"</span><span class="pln"> </span><span class=
"pun">+</span><span class="pln"> services</span><span class="pun">[</span><span class="lit">0</span><span class=
"pun">].</span><span class="pln">name </span><span class="pun">+</span><span class="pln"> </span><span class=
"str">" event received: "</span><span class="pun">;</span><span class="pln">
         debug</span><span class="pun">.</span><span class="pln">textContent </span><span class=
"pun">+=</span><span class="pln"> msg</span><span class="pun">.</span><span class="pln">data</span><span class=
"pun">;</span><span class="pln">
    </span><span class="pun">},</span><span class="pln"> </span><span class="kwd">false</span><span class=
"pun">);</span><span class="pln">

 </span><span class="com">// Send a control signal to mute the service audio</span><span class="pln">

    </span><span class="kwd">var</span><span class="pln"> svcXhr </span><span class="pun">=</span><span class=
"pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">XMLHttpRequest</span><span class=
"pun">();</span><span class="pln">
    svcXhr</span><span class="pun">.</span><span class="pln">open</span><span class="pun">(</span><span class=
"str">"POST"</span><span class="pun">,</span><span class="pln"> services</span><span class="pun">[</span><span class=
"lit">0</span><span class="pun">].</span><span class="pln">url</span><span class="pun">);</span><span class=
"pln"> </span><span class="com">// services[0].url and its sub-resources are</span><span class="pln">
                                          </span><span class=
"com">// available for cross-site XHR use.</span><span class="pln">

    svcXhr</span><span class="pun">.</span><span class="pln">setRequestHeader</span><span class=
"pun">(</span><span class="str">'SOAPAction'</span><span class="pun">,</span><span class="pln"> </span><span class=
"str">'urn:schemas-upnp-org:service:RenderingControl:1#SetMute'</span><span class="pun">);</span><span class="pln">
    svcXhr</span><span class="pun">.</span><span class="pln">setRequestHeader</span><span class=
"pun">(</span><span class="str">'Content-Type'</span><span class="pun">,</span><span class="pln"> </span><span class=
"str">'text/xml; charset="utf-8";'</span><span class="pun">);</span><span class="pln">

    svcXhr</span><span class="pun">.</span><span class="pln">onreadystatechange </span><span class=
"pun">=</span><span class="pln"> </span><span class="kwd">function</span><span class="pln"> </span><span class=
"pun">(</span><span class="pln"> response </span><span class="pun">)</span><span class="pln"> </span><span class=
"pun">{</span><span class="pln">
      </span><span class="kwd">if</span><span class="pun">(</span><span class="pln"> response</span><span class=
"pun">.</span><span class="pln">readyState </span><span class="pun">!=</span><span class="pln"> </span><span class=
"lit">4</span><span class="pln"> </span><span class="pun">||</span><span class="pln"> response</span><span class=
"pun">.</span><span class="pln">status </span><span class="pun">!=</span><span class="pln"> </span><span class=
"lit">200</span><span class="pln"> </span><span class="pun">)</span><span class="pln">
        </span><span class="kwd">return</span><span class="pun">;</span><span class="pln">
      debug</span><span class="pun">.</span><span class="pln">innerHTML </span><span class="pun">+=</span><span class=
"pln"> </span><span class="str">"&lt;br&gt;"</span><span class="pln"> </span><span class="pun">+</span><span class=
"pln"> services</span><span class="pun">[</span><span class="lit">0</span><span class="pun">].</span><span class=
"pln">name </span><span class="pun">+</span><span class="pln"> </span><span class=
"str">" response received: "</span><span class="pun">;</span><span class="pln">
      debug</span><span class="pun">.</span><span class="pln">textContent </span><span class=
"pun">+=</span><span class="pln"> response</span><span class="pun">.</span><span class=
"pln">responseXML</span><span class="pun">;</span><span class="pln">
    </span><span class="pun">}</span><span class="pln">

    </span><span class="com">// Service messaging to mute the provided service</span><span class="pln">
    </span><span class="kwd">var</span><span class="pln"> svcMsg </span><span class="pun">=</span><span class=
"pln"> </span><span class="str">'&lt;?xml version="1.0" encoding="utf-8"?&gt;'</span><span class=
"pln"> </span><span class="pun">+</span><span class="pln">
                 </span><span class=
"str">'&lt;s:Envelope s:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" '</span><span class=
"pln"> </span><span class="pun">+</span><span class="pln">
                   </span><span class=
"str">'xmlns:s="http://schemas.xmlsoap.org/soap/envelope/"&gt;'</span><span class="pln"> </span><span class=
"pun">+</span><span class="pln">
                   </span><span class="str">'&lt;s:Body&gt;'</span><span class="pln"> </span><span class=
"pun">+</span><span class="pln">
                     </span><span class=
"str">'&lt;u:SetMute xmlns:u="urn:schemas-upnp-org:service:RenderingControl:1"&gt;'</span><span class=
"pln"> </span><span class="pun">+</span><span class="pln">
                       </span><span class="str">'&lt;InstanceID&gt;0&lt;/InstanceID&gt;'</span><span class=
"pln"> </span><span class="pun">+</span><span class="pln">
                       </span><span class="str">'&lt;Channel&gt;Master&lt;/Channel&gt;'</span><span class=
"pln"> </span><span class="pun">+</span><span class="pln">
                       </span><span class="str">'&lt;DesiredMute&gt;true&lt;/DesiredMute&gt;'</span><span class=
"pln"> </span><span class="pun">+</span><span class="pln">
                     </span><span class="str">'&lt;/u:SetMute&gt;'</span><span class="pln"> </span><span class=
"pun">+</span><span class="pln">
                   </span><span class="str">'&lt;/s:Body&gt;'</span><span class="pln"> </span><span class=
"pun">+</span><span class="pln">
                 </span><span class="str">'&lt;/s:Envelope&gt;'</span><span class="pun">;</span><span class="pln">

    svcXhr</span><span class="pun">.</span><span class="pln">send</span><span class="pun">(</span><span class=
"pln">svcMsg</span><span class="pun">);</span><span class="pln">
    debug</span><span class="pun">.</span><span class="pln">innerHTML </span><span class="pun">+=</span><span class=
"pln"> </span><span class="str">"&lt;br&gt;"</span><span class="pln"> </span><span class="pun">+</span><span class=
"pln"> services</span><span class="pun">[</span><span class="lit">0</span><span class="pun">].</span><span class=
"pln">name </span><span class="pun">+</span><span class="pln"> </span><span class=
"str">" request sent: "</span><span class="pun">;</span><span class="pln">
    debug</span><span class="pun">.</span><span class="pln">textContent </span><span class="pun">+=</span><span class=
"pln"> svcMsg</span><span class="pun">;</span><span class="pln">
  </span><span class="pun">}</span><span class="pln">

  </span><span class="kwd">function</span><span class="pln"> errorCallback</span><span class="pun">(</span><span class=
"pln"> error </span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
    debug</span><span class="pun">.</span><span class="pln">innerHTML </span><span class="pun">+=</span><span class=
"pln"> </span><span class="str">"&lt;br&gt;An error occurred: "</span><span class="pln"> </span><span class=
"pun">+</span><span class="pln"> error</span><span class="pun">.</span><span class="pln">name</span><span class=
"pun">;</span><span class="pln">
  </span><span class="pun">}</span><span class="pln">
</span><span class="tag">&lt;/script&gt;</span>
</pre>
      </div>
    </section>
    <section id="acknowledgements">
      <h2 aria-level="1"
          role="heading"
          id="h2_acknowledgements">
        <span class="secno">B.</span> Acknowledgements
      </h2>
      <p>
        Thanks are expressed by the editor to the following individuals for their feedback on this specification to
        date (in alphabetical order):<br>
        <br>
        Adam Barth, Gar Bergstedt, Robin Berjon, Lars-Erik Bolstad, Marcos Caceres, Cathy Chan, Daniel Danciu,
        Jean-Claude Dufourd, Youenn Fablot, Mark Foltz, Dominique Hazael-Massieux, Frederick Hirsch, Tatsuya Igarashi,
        Hari G Kumar, Bob Lund, Giuseppe Pascale, Marcin Simonides, Clarke Stevens, Christian Söderström, Mark Vickers.
      </p>
      <p>
        Thanks are also expressed by the editor to the following organizations and groups for their support in
        producing this specification to date (in alphabetical order):<br>
        <br>
        CableLabs, Google Inc., Opera Software ASA, Nokia Corp., Télécom ParisTech, <abbr title=
        "World Wide Web Consortium">W3C</abbr> Device APIs Working Group, <abbr title=
        "World Wide Web Consortium">W3C</abbr> Web and TV Interest Group.
      </p>
    </section><style>
a.externalDFN { color: #00C; border-bottom: 1px dashed #00C; }
    a.internalDFN { color: #00C; text-decoration: solid; }
    </style>
    <section id="references"
             class="appendix"
             typeof="bibo:Chapter"
             resource="#ref"
             rel="bibo:Chapter">
      <h2 aria-level="1"
          role="heading"
          id="h2_references">
        <span class="secno">C.</span> References
      </h2>
      <section id="normative-references"
               typeof="bibo:Chapter"
               resource="#ref"
               rel="bibo:Chapter">
        <h3 aria-level="2"
            role="heading"
            id="h3_normative-references">
          <span class="secno">C.1</span> Normative references
        </h3>
        <dl class="bibliography"
            about="">
          <dt id="bib-CORS">
            [CORS]
          </dt>
          <dd rel="dcterms:requires">
            Anne van Kesteren. <a href="http://www.w3.org/TR/cors/"><cite>Cross-Origin Resource Sharing</cite></a>. 29
            January 2013. W3C Candidate Recommendation. URL: <a href=
            "http://www.w3.org/TR/cors/">http://www.w3.org/TR/cors/</a>
          </dd>
          <dt id="bib-DNS-SD">
            [DNS-SD]
          </dt>
          <dd rel="dcterms:requires">
            S. Cheshire; M. Krochmal. <a href="http://www.ietf.org/rfc/rfc6763.txt"><cite>DNS-Based Service
            Discovery</cite></a>. February 2013. RFC. URL: <a href=
            "http://www.ietf.org/rfc/rfc6763.txt">http://www.ietf.org/rfc/rfc6763.txt</a>
          </dd>
          <dt id="bib-DOM4">
            [DOM4]
          </dt>
          <dd rel="dcterms:requires">
            Anne van Kesteren; Aryeh Gregor; Lachlan Hunt; Ms2ger. <a href=
            "http://www.w3.org/TR/dom/"><cite>DOM4</cite></a>. 6 December 2012. W3C Working Draft. URL: <a href=
            "http://www.w3.org/TR/dom/">http://www.w3.org/TR/dom/</a>
          </dd>
          <dt id="bib-HTML5">
            [HTML5]
          </dt>
          <dd rel="dcterms:requires">
            Robin Berjon; Steve Faulkner; Travis Leithead; Erika Doyle Navara; Edward O'Connor; Silvia Pfeiffer.
            <a href="http://www.w3.org/TR/html5/"><cite>HTML5</cite></a>. 6 August 2013. W3C Candidate Recommendation.
            URL: <a href="http://www.w3.org/TR/html5/">http://www.w3.org/TR/html5/</a>
          </dd>
          <dt id="bib-MDNS">
            [MDNS]
          </dt>
          <dd rel="dcterms:requires">
            S. Cheshire; M. Krochmal. <a href="http://www.ietf.org/rfc/rfc6763.txt"><cite>Multicast DNS</cite></a>.
            February 2013. RFC. URL: <a href=
            "http://www.ietf.org/rfc/rfc6763.txt">http://www.ietf.org/rfc/rfc6763.txt</a>
          </dd>
          <dt id="bib-RFC2119">
            [RFC2119]
          </dt>
          <dd rel="dcterms:requires">
            S. Bradner. <a href="http://www.ietf.org/rfc/rfc2119.txt"><cite>Key words for use in RFCs to Indicate
            Requirement Levels.</cite></a> March 1997. Internet RFC 2119. URL: <a href=
            "http://www.ietf.org/rfc/rfc2119.txt">http://www.ietf.org/rfc/rfc2119.txt</a>
          </dd>
          <dt id="bib-UPNP-DEVICEARCH11">
            [UPNP-DEVICEARCH11]
          </dt>
          <dd rel="dcterms:requires">
            <a href="http://upnp.org/specs/arch/UPnP-arch-DeviceArchitecture-v1.1.pdf"><cite>UPnP Device Architecture
            1.1</cite></a>. 15 October 2008. UPnP Forum. PDF document. URL: <a href=
            "http://upnp.org/specs/arch/UPnP-arch-DeviceArchitecture-v1.1.pdf">http://upnp.org/specs/arch/UPnP-arch-DeviceArchitecture-v1.1.pdf</a>
          </dd>
          <dt id="bib-WEBIDL">
            [WEBIDL]
          </dt>
          <dd rel="dcterms:requires">
            Cameron McCormack. <a href="http://www.w3.org/TR/WebIDL/"><cite>Web IDL</cite></a>. 19 April 2012. W3C
            Candidate Recommendation. URL: <a href="http://www.w3.org/TR/WebIDL/">http://www.w3.org/TR/WebIDL/</a>
          </dd>
        </dl>
      </section>
      <section id="informative-references"
               typeof="bibo:Chapter"
               resource="#ref"
               rel="bibo:Chapter">
        <h3 aria-level="2"
            role="heading"
            id="h3_informative-references">
          <span class="secno">C.2</span> Informative references
        </h3>
        <dl class="bibliography"
            about="">
          <dt id="bib-hnreq">
            [hnreq]
          </dt>
          <dd rel="dcterms:references">
            Giuseppe Pascale. <a href="http://www.w3.org/TR/hnreq/"><cite>Requirements for Home Networking
            Scenarios</cite></a>. 1 December 2011. W3C Note. URL: <a href=
            "http://www.w3.org/TR/hnreq/">http://www.w3.org/TR/hnreq/</a>
          </dd>
        </dl>
      </section>
    </section>
  </body>
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