discovery-api/Overview.src.html
author Rich Tibbett <richt@opera.com>
Fri, 08 Feb 2013 14:59:37 +0100
changeset 387 abb49f62a775
parent 378 89d1cef16d35
child 388 f6ad389be556
permissions -rw-r--r--
Clarify the terms 'new service', 'existing service' and 'current service'
     1 <!DOCTYPE html>
     2 <!--
     3 
     4   THIS IS THE WORKING VERSION OF THE CURRENT SPECIFICATION!
     5 
     6   This specification is built using ReSpec.js <http://dev.w3.org/2009/dap/ReSpec.js/documentation.html>
     7 
     8   From time to time it's necessary to HTML5 Tidy this document using the tool @ <http://w3c.github.com/tidy-html5/>.
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    10   The command used to format this document (Overview.src.html) is as follows (replacing all = signs with - signs!):
    11 
    12   @> tidy ==new-blocklevel-tags section ==char-encoding utf8 ==tidy-mark no ==indent yes ==indent-spaces 2 ==indent-attributes yes ==wrap 120 ==fix-bad-comments yes -m Overview.src.html
    13 
    14   To publish a new compiled version (Overview.html), we need to open this file (Overview.src.html) in any web browser.
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    20   Next we run HTML5 Tidy over our new Overview.html file with the following command (replacing all = signs with - signs!):
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    22   @> tidy ==new-blocklevel-tags section ==char-encoding utf8 ==tidy-mark no ==indent yes ==indent-spaces 2 ==indent-attributes yes ==wrap 120 ==hide-comments yes -m Overview.html
    23 
    24   Now the specification is ready to be published :)
    25 
    26 -->
    27 <html>
    28   <head>
    29     <title>
    30       Network Service Discovery
    31     </title>
    32     <meta http-equiv='Content-Type'
    33           content='text/html; charset=utf-8'>
    34     <script type="text/javascript"
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    36 var respecConfig = {
    37           specStatus:   "ED",
    38           //publishDate:  "2012-10-04",
    39           shortName:    "discovery-api",
    40           edDraftURI:   "http://dvcs.w3.org/hg/dap/raw-file/tip/discovery-api/Overview.html",
    41           previousMaturity: "FPWD",
    42           previousPublishDate: "2012-08-07",
    43           editors: [
    44             {
    45               name:       "Rich Tibbett",
    46               //url:        "http://richt.me/",
    47               company:    "Opera Software ASA",
    48               companyURL: "http://opera.com/"
    49             },
    50             {
    51               name:       "Clarke Stevens",
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    55             }
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   100     </style>
   101   </head>
   102   <body>
   103     <section id='abstract'>
   104       <p>
   105         This specification defines a mechanism for an HTML document to discover and subsequently communicate with
   106         <abbr title="Hypertext Transfer Protocol">HTTP</abbr>-based services advertised via common discovery protocols
   107         within the current network.
   108       </p>
   109     </section>
   110     <section id='sotd'>
   111       <p>
   112         This document represents the early consensus of the group on the scope and features of the proposed API.
   113       </p>
   114     </section>
   115     <section class="informative">
   116       <h3>
   117         Introduction
   118       </h3>
   119       <p>
   120         To enable Web pages to connect and communicate with Local-networked Services provided over HTTP, this
   121         specification introduces the <a href="#navigatornetworkservice"><code>NavigatorNetworkService</code></a>
   122         interface.
   123       </p>
   124       <p>
   125         Using this <abbr title="Application Programming Interface">API</abbr> consists of requesting a well-known
   126         service type, known by developers and advertised by Local-networked Devices. User authorization, where the user
   127         connects the web page to discovered services, is expected before the web page is able to interact with any
   128         Local-networked Services.
   129       </p>
   130       <p>
   131         A web page creates a request to obtain connectivity to services running in the network by specifying a
   132         well-known discovery service type that it wishes to interact with.
   133       </p>
   134       <p>
   135         The user agent, having captured all advertised services on the network from the <a>service discovery
   136         mechanisms</a> included in this recommendation, attempts to match the requested service type to a discovered
   137         service according to the processing described herein.
   138       </p>
   139       <p>
   140         If a service connectivity request is successful then the Web page is provided with the necessary information to
   141         communicate with the authorized Local-networked Service. If the request fails then the Web page will receive an
   142         error callback containing an error code describing the cause of Local-networked Service connectivity failure.
   143       </p>
   144       <p>
   145         Once connected to a Local-networked Service the Web page can send requests and receive responses to the
   146         Local-networked Service via the messaging format and appropriate channel inferred from the service type
   147         authorized via the provided API. The Web page, once connected, can also receive service-pushed events, in the
   148         messaging format supported by the Local-networked Device, if such event subscription functionality is provided
   149         by the connected Local-networked Service.
   150       </p>
   151       <div class="example">
   152         <p>
   153           Example of requesting a DNS-SD advertised service:
   154         </p>
   155         <hr>
   156         <pre class="highlight">
   157 function showServices( services ) {
   158   // Show a list of all the services provided to the web page
   159   for(var i = 0, l = services.length; i &lt; l; i++) console.log( services[i].name );
   160 }
   161 
   162 navigator.getNetworkServices('zeroconf:_boxee-jsonrpc._tcp', showServices);
   163 </pre>
   164       </div>
   165       <div class="example">
   166         <p>
   167           Example of requesting a UPnP advertised service, also handling error conditions:
   168         </p>
   169         <hr>
   170         <pre class="highlight">
   171 function showServices( services ) {
   172   // Show a list of all the services provided to the web page
   173   for(var i = 0, l = services.length; i &lt; l; i++) console.log( services[i].name );
   174 }
   175 
   176 function error( e ) {
   177   console.log( "Error occurred: " + e.code );
   178 }
   179 
   180 navigator.getNetworkServices('upnp:urn:schemas-upnp-org:service:ContentDirectory:1', showServices, error);
   181 </pre>
   182       </div>
   183       <div class="example">
   184         <p>
   185           Example of requesting either a DNS-SD or UPnP advertised service:
   186         </p>
   187         <hr>
   188         <pre class="highlight">
   189 function showServices( services ) {
   190   // Show a list of all the services provided to the web page (+ service type)
   191   for(var i = 0, l = services.length; i &lt; l; i++)
   192      console.log( services[i].name + '(' + services[i].type + ')' );
   193 }
   194 
   195 navigator.getNetworkServices([
   196   'zeroconf:_boxee-jsonrpc._tcp',
   197   'upnp:urn:schemas-upnp-org:service:ContentDirectory:1'
   198 ], showServices);
   199 </pre>
   200       </div>
   201       <p>
   202         For more detailed examples see the <a href="#examples">Examples</a> section.
   203       </p>
   204     </section>
   205     <section id='conformance'>
   206       <p>
   207         Requirements phrased in the imperative as part of algorithms (such as "strip any leading space characters" or
   208         "return false and abort these steps") are to be interpreted with the meaning of the key word ("must", "should",
   209         "may", etc) used in introducing the algorithm.
   210       </p>
   211       <p>
   212         Some conformance requirements are phrased as requirements on attributes, methods or objects. Such requirements
   213         are to be interpreted as requirements on user agents.
   214       </p>
   215       <p>
   216         Conformance requirements phrased as algorithms or specific steps MAY be implemented in any manner, so long as
   217         the end result is equivalent. (In particular, the algorithms defined in this specification are intended to be
   218         easy to follow, and not intended to be performant.)
   219       </p>
   220       <p>
   221         The only conformance class defined by this specification is a <dfn>user agent</dfn>.
   222       </p>
   223       <p>
   224         User agents MAY impose implementation-specific limits on otherwise unconstrained inputs, e.g. to prevent denial
   225         of service attacks, to guard against running out of memory, or to work around platform-specific limitations.
   226       </p>
   227       <p>
   228         When support for a feature is disabled (e.g. as an emergency measure to mitigate a security problem, or to aid
   229         in development, or for performance reasons), user agents MUST act as if they had no support for the feature
   230         whatsoever, and as if the feature was not mentioned in this specification. For example, if a particular feature
   231         is accessed via an attribute in a Web IDL interface, the attribute itself would be omitted from the objects
   232         that implement that interface - leaving the attribute on the object but making it return null or throw an
   233         exception is insufficient.
   234       </p>
   235       <section>
   236         <h3>
   237           Dependencies
   238         </h3>This specification relies on several other underlying specifications.
   239         <dl>
   240           <dt>
   241             HTML
   242           </dt>
   243           <dd>
   244             Many fundamental concepts from HTML are used by this specification. [[!HTML5]]
   245           </dd>
   246           <dt>
   247             WebIDL
   248           </dt>
   249           <dd>
   250             The IDL blocks in this specification use the semantics of the WebIDL specification. [[!WEBIDL]]
   251           </dd>
   252         </dl>
   253       </section>
   254     </section>
   255     <section>
   256       <h3>
   257         Terminology
   258       </h3>
   259       <p>
   260         The construction "a <code>Foo</code> object", where <code>Foo</code> is actually an interface, is sometimes
   261         used instead of the more accurate "an object implementing the interface <code>Foo</code>".
   262       </p>
   263       <p>
   264         The term DOM is used to refer to the API set made available to scripts in Web applications, and does not
   265         necessarily imply the existence of an actual <code>Document</code> object or of any other <code>Node</code>
   266         objects as defined in the DOM Core specifications. [[!DOM4]]
   267       </p>
   268       <p>
   269         An IDL attribute is said to be <em>getting</em> when its value is being retrieved (e.g. by author script), and
   270         is said to be <em>setting</em> when a new value is assigned to it.
   271       </p>
   272       <p>
   273         A <dfn>valid service type</dfn> is any of the following:
   274       </p>
   275       <ul>
   276         <li>a string that begins with <code>upnp:</code> or <code>zeroconf:</code> followed by one or more characters
   277         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,
   278         U+005E to U+007E.
   279         </li>
   280         <li>a string that begins with <code>dial:</code> followed by an integer version.
   281         </li>
   282       </ul>
   283       <p>
   284         A <a>valid service type</a> provided in the <code>type</code> attribute of the <a href=
   285         "#dom-navigator-getnetworkservices"><code>getNetworkServices()</code></a> method will be matched against the
   286         services currently contained in the <a>list of available service records</a> according to the algorithms
   287         defined in this specification.
   288       </p>
   289       <p>
   290         A <dfn>user-agent generated callback url</dfn> is a Local-network accessible URL endpoint that a <a>user
   291         agent</a> generates and maintains for receiving HTTP NOTIFY requests from UPnP Event sources. It is only
   292         required when the user agent implements UPnP Service Discovery as defined in this specification.
   293       </p>
   294       <p>
   295         In this specification we use the following terms to describe the processes required for Local-networked
   296         Services management:
   297       </p>
   298       <ul>
   299         <li>A <dfn>new service</dfn> is a Local-networked Service that has not previously been discovered or registered
   300         in the <a>list of available service records</a>.
   301         </li>
   302         <li>An <dfn>existing service</dfn> is a Local-networked Service that has previously been discovered and is
   303         registered in the <a>list of available service records</a>.
   304         </li>
   305         <li>A <dfn>current service</dfn> is a Local-networked Service, represented by a <a href=
   306         "#networkservice"><code>NetworkService</code></a> object, that is currently being shared with a web page via a
   307         <a href="#networkservices"><code>NetworkServices</code></a> object registered in the <a>list of active service
   308         managers</a>.
   309         </li>
   310       </ul>
   311     </section>
   312     <section>
   313       <h2>
   314         Requesting networked services
   315       </h2>
   316       <pre class="widl">
   317 [Supplemental, NoInterfaceObject]
   318 interface <dfn id="navigatornetworkservice">NavigatorNetworkService</dfn> {
   319   // Obtain a Local-networked Service
   320   void <a href="#dom-navigator-getnetworkservices">getNetworkServices</a>( in any type,
   321                            in <a href=
   322 "#navigatornetworkservicesuccesscallback">NavigatorNetworkServiceSuccessCallback</a> successCallback,
   323                            in optional <a href=
   324 "#navigatornetworkserviceerrorcallback">NavigatorNetworkServiceErrorCallback</a> errorCallback );
   325 };
   326 <a class="externalDFN"
   327      href=
   328      "http://www.whatwg.org/specs/web-apps/current-work/complete/timers.html#navigator">Navigator</a> implements <a href=
   329      "#navigatornetworkservice">NavigatorNetworkService</a>;
   330 
   331 [Callback=FunctionOnly, NoInterfaceObject]
   332 interface <dfn id="navigatornetworkservicesuccesscallback">NavigatorNetworkServiceSuccessCallback</dfn> {
   333   void handleEvent( in <a href="#networkservices">NetworkServices</a> services );
   334 };
   335 
   336 [NoInterfaceObject]
   337 interface <dfn id="navigatornetworkserviceerror">NavigatorNetworkServiceError</dfn> {
   338   const unsigned short <a href="#dom-navigatornetworkserviceerror-permission_denied">PERMISSION_DENIED_ERR</a> = 1;
   339   const unsigned short <a href="#dom-navigatornetworkserviceerror-unknown_type_prefix">UNKNOWN_TYPE_PREFIX_ERR</a> = 2;
   340   readonly attribute unsigned short <a href="#dom-navigatornetworkserviceerror-code">code</a>;
   341 };
   342 
   343 [Callback=FunctionOnly, NoInterfaceObject]
   344 interface <dfn id="navigatornetworkserviceerrorcallback">NavigatorNetworkServiceErrorCallback</dfn> {
   345   void handleEvent( in <a href="#navigatornetworkserviceerror">NavigatorNetworkServiceError</a> error );
   346 };
   347 </pre>
   348       <section>
   349         <h2>
   350           Methods
   351         </h2>
   352         <dl class="domintro">
   353           <dt>
   354             <var title="">window</var> . <code title="dom-navigator"><a href=
   355             "http://www.whatwg.org/specs/web-apps/current-work/complete/timers.html#navigator">navigator</a></code> .
   356             <code title="dom-navigator-getNetworkServices"><a href=
   357             "#dom-navigator-getnetworkservices">getNetworkServices</a></code> ( <var title="">type</var> , <var title=
   358             "">successCallback</var> [, <var title="">errorCallback</var> ] )
   359           </dt>
   360           <dd>
   361             <p>
   362               Prompts the user to select discovered network services that have advertised support for the requested
   363               service type.
   364             </p>
   365             <p>
   366               The <var title="">type</var> argument contains one or more <a>valid service type</a> tokens that the web
   367               page would like to interact with.
   368             </p>
   369             <p>
   370               If the user accepts, the <var title="">successCallback</var> is invoked, with zero or more <a href=
   371               "#networkservice"><code>NetworkService</code></a> objects as its argument.
   372             </p>
   373             <p>
   374               If the user declines, the <var title="">errorCallback</var> (if any) is invoked.
   375             </p>
   376           </dd>
   377         </dl>
   378         <div>
   379           <p>
   380             When the <dfn id="dom-navigator-getnetworkservices"
   381                title="dom-navigator-getnetworkservices"><code>getNetworkServices(type, successCallback[,
   382                errorCallback])</code></dfn> method is called, the <a>user agent</a> MUST run the following steps:
   383           </p>
   384           <ol class="rule">
   385             <li>Let <var>requested control types</var> be initially set to an empty array.
   386             </li>
   387             <li>If <var>type</var> is an array consisting of one or more <a>valid service type</a> tokens, then let
   388             <var>requested control types</var> by the value of <var>type</var>, removing any non-<a>valid service
   389             type</a> tokens from the resulting array.
   390             </li>
   391             <li>If <var>type</var> is a string consisting of one <a>valid service type</a> token, then let
   392             <var>requested control types</var> be an array containing one item with a value of <var>type</var>.
   393             </li>
   394             <li>If <var>requested control types</var> is an array that contains at least one or more <a title=
   395             "valid service type">valid service type</a> tokens then continue to the step labeled <em>process</em>
   396             below. Otherwise, the <a>user agent</a> MUST <a href=
   397             "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
   398                   class="externalDFN">queue a task</a> to invoke <var>errorCallback</var>, if it is provided and is an
   399                   object of type <code>Function</code>, with a new <a href=
   400                   "#navigatornetworkserviceerror"><code>NavigatorNetworkServiceError</code></a> object whose <a href=
   401                   "#dom-navigatornetworkserviceerror-code"><code>code</code></a> attribute has the numeric value 2
   402                   (<a href=
   403                   "#dom-navigatornetworkserviceerror-unknown_type_prefix"><code>UNKNOWN_TYPE_PREFIX_ERR</code></a>) as
   404                   its argument, abort any remaining steps and return.
   405             </li>
   406             <li>
   407               <em>Process</em>: Let <var>services found</var> be an empty array.
   408             </li>
   409             <li>For each <var>available service</var> in the <a>list of available service records</a> run the following
   410             steps:
   411               <ol class="rule">
   412                 <li>For each <var>requested control type</var> in <var>requested control types</var>: If <var>available
   413                 service</var>'s <code>type</code> attribute equals the <var>requested control type</var> then let <var>
   414                   matched service</var> equal the value of <var>available service</var> and continue at the step
   415                   labeled <var>attach</var> below.
   416                 </li>
   417                 <li>Continue at the next <var>available service</var>.
   418                 </li>
   419                 <li>
   420                   <em>Attach</em>: If <var>matched service</var> is not empty then run the following steps:
   421                   <ol class="rule">
   422                     <li>Let <var>new service object</var> be a new <a href=
   423                     "#networkservice"><code>NetworkService</code></a> object, mapping the parameters of <var>matched
   424                     service</var> to this new object where possible.
   425                     </li>
   426                     <li>Append <var>new service object</var> to the <var>services found</var> array.
   427                     </li>
   428                   </ol>
   429                 </li>
   430               </ol>
   431             </li>
   432             <li>Return, and run the remaining steps asynchronously.
   433             </li>
   434             <li>Optionally, e.g. based on a previously-established user preference, for security reasons, or due to
   435             platform limitations, the <a>user agent</a> MAY <a href=
   436             "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
   437                   class="externalDFN">queue a task</a> to invoke <var>errorCallback</var>, if it is provided and is an
   438                   object of type <code>Function</code>, with a new <a href=
   439                   "#navigatornetworkserviceerror"><code>NavigatorNetworkServiceError</code></a> object whose <a href=
   440                   "#dom-navigatornetworkserviceerror-code"><code>code</code></a> attribute has the numeric value 1
   441                   (<a href=
   442                   "#dom-navigatornetworkserviceerror-permission_denied"><code>PERMISSION_DENIED_ERR</code></a>) as its
   443                   argument, abort any remaining steps and return.
   444             </li>
   445             <li>The user agent MUST NOT provide the entry script's origin with a <a href=
   446             "#networkservices"><code>NetworkServices</code></a> object without prior permission given by the user.
   447               <p>
   448                 If <var>services found</var> is not an empty array then the <a>user agent</a> MAY choose to prompt the
   449                 user in a user-agent-specific manner for permission to provide the <a href=
   450                 "http://www.whatwg.org/specs/web-apps/current-work/complete/browsers.html#entry-script"
   451                    class="externalDFN">entry script</a>'s <a href=
   452                    "http://www.whatwg.org/specs/web-apps/current-work/complete/origin-0.html#origin"
   453                    class="externalDFN">origin</a> with a <a href="#networkservices"><code>NetworkServices</code></a>
   454                    object representing the <a>user-authorized</a> subset of <var>services found</var>.
   455               </p>
   456               <p>
   457                 Alternatively, the user agent MAY choose to queue a task to invoke <var>successCallback</var> or
   458                 <var>errorCallback</var> immediately based on a previously-established user preference, for security
   459                 reasons, or due to platform limitations. In such an implementation, if <var>successCallback</var> is to
   460                 be fired as a result of a previously-established user preference then the <a>user agent</a> MUST
   461                 continue at the next step of this algorithm.
   462               </p>
   463               <p>
   464                 If permission has been granted by the user to access one or more networked services then the <a>user
   465                 agent</a> SHOULD include an "ongoing local-network communication" indicator.
   466               </p>
   467               <p>
   468                 If permission has been denied by the user, <a>user agent</a> or platform, then the <a>user agent</a>
   469                 MUST <a href="http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
   470                    class="externalDFN">queue a task</a> to invoke <var>errorCallback</var>, if it is provided and is an
   471                    object of type <code>Function</code>, with a new <a href=
   472                    "#navigatornetworkserviceerror"><code>NavigatorNetworkServiceError</code></a> object whose <a href=
   473                    "#dom-navigatornetworkserviceerror-code"><code>code</code></a> attribute has the numeric value 1
   474                    (<a href=
   475                    "#dom-navigatornetworkserviceerror-permission_denied"><code>PERMISSION_DENIED_ERR</code></a>) as its
   476                    argument, abort any remaining steps and return.
   477               </p>
   478               <p>
   479                 If the user never responds or no previously-established user preference has been met, this algorithm
   480                 stalls on this step.
   481               </p>
   482             </li>
   483             <li>Let <var>services</var> be an empty array.
   484             </li>
   485             <li>If <var>services found</var> is not an empty array then set <var>services</var> to be an array of one
   486             or more <a href="#networkservice"><code>NetworkService</code></a> objects for which the user granted
   487             permission above - known as the current objects <dfn>user-authorized</dfn> services.
   488             </li>
   489             <li>Remove all previously whitelisted urls from the <a>entry script origin's URL whitelist</a> granted in
   490             the current <a href="http://www.whatwg.org/specs/web-apps/current-work/complete/browsers.html#entry-script"
   491                   class="externalDFN">entry script</a>'s <a href=
   492                   "http://www.whatwg.org/specs/web-apps/current-work/complete/origin-0.html#origin"
   493                   class="externalDFN">origin</a>.
   494             </li>
   495             <li>For each Object <var>service</var> in <var>services</var>, if any, run the following sub-steps:
   496               <ol class="rule">
   497                 <li>Add the <var>service</var>'s <code>url</code> parameter to the <a>entry script origin's
   498                   <abbr title="Uniform Resource Locator">URL</abbr> whitelist</a>.
   499                 </li>
   500                 <li>If <var>service</var>'s <code>type</code> parameter begins with the DOMString "<code>upnp:</code>"
   501                 and the <var>service</var>'s <code>eventsUrl</code> parameter is not empty then <a>setup a UPnP Events
   502                 Subscription</a> for <var>service</var>.
   503                 </li>
   504               </ol>
   505             </li>
   506             <li>Let <var>services manager</var> be a new <a href="#networkservices"><code>NetworkServices</code></a>
   507             object.
   508             </li>
   509             <li>Store <var>requested control types</var> against <var>services manager</var> as an internal variable.
   510             </li>
   511             <li>Set <var>services manager</var>'s <a href=
   512             "#dom-networkservices-servicesavailable"><code>servicesAvailable</code></a> attribute to the number of
   513             items currently found in the <a>list of available service records</a> whose <code>type</code> property
   514             matches any of the tokens requested in <var>requested control types</var>.
   515             </li>
   516             <li>Add <var>services</var>, if any, to the <var>services manager</var> object as its collection of
   517             <a>indexed properties</a>. If <var>services</var> is an empty array then the <var>services manager</var>
   518             does not have any <var>indexed properties</var>.
   519             </li>
   520             <li>Set <var>services manager</var>'s <a href="#dom-networkservices-length"><code>length</code></a>
   521             attribute to the number of items in <var>services</var>.
   522             </li>
   523             <li>Add <var>services manager</var> to the <a>list of active service managers</a>.
   524             </li>
   525             <li>The <a>user agent</a> MUST <a href=
   526             "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
   527                   class="externalDFN">queue a task</a> to invoke <var>successCallback</var> with <var>services
   528                   manager</var> as its argument.
   529             </li>
   530           </ol>
   531           <p>
   532             The <a href="http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#task-source"
   533                class="externalDFN">task source</a> for these <a href=
   534                "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#concept-task"
   535                class="externalDFN">tasks</a> is the <a href=
   536                "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#user-interaction-task-source"
   537                class="externalDFN">user interaction task source</a>.
   538           </p>
   539           <p>
   540             When a <a href="#networkservice"><code>NetworkService</code></a> object is provided to a Web page, the
   541             <a>user agent</a> MUST add the <code>url</code> property to the <dfn>entry script origin's URL
   542             whitelist</dfn>. This list enables the Web page to override and initiate cross-site resource requests
   543             towards these URLs, and any sub-resources of these URLs, within the current <a href=
   544             "http://www.whatwg.org/specs/web-apps/current-work/complete/browsers.html#entry-script"
   545                class="externalDFN">entry script</a>'s <a href=
   546                "http://www.whatwg.org/specs/web-apps/current-work/complete/origin-0.html#origin"
   547                class="externalDFN">origin</a> via various existing mechanisms (e.g. Web Sockets, Server-Sent Events,
   548                Web Messaging, XMLHttpRequest).
   549           </p>
   550           <p>
   551             If the user navigates away from the <a href=
   552             "http://www.whatwg.org/specs/web-apps/current-work/complete/browsers.html#entry-script"
   553                class="externalDFN">entry script</a>'s <a href=
   554                "http://www.whatwg.org/specs/web-apps/current-work/complete/origin-0.html#origin"
   555                class="externalDFN">origin</a> then the <a>user agent</a> <em class="ct">MUST</em> remove all previously
   556                whitelisted urls from the <a>entry script origin's URL whitelist</a>. There is no persistence to network
   557                service selections provided to a web page. It is not possible to access a previously white-listed
   558                networked service without the necessary user authorization in all of the following cases:
   559           </p>
   560           <ul>
   561             <li>If the current script is reloaded at any point in the same or different window.
   562             </li>
   563             <li>if the current script reinvokes the <a href=
   564             "#dom-navigator-getnetworkservices"><code>getNetworkServices()</code></a> method at any point in its
   565             execution.
   566             </li>
   567             <li>If the user navigates forward or back in their history to reload the current page.
   568             </li>
   569             <li>If a script is running in a different origin.
   570             </li>
   571           </ul>
   572         </div>
   573       </section>
   574       <section>
   575         <h3>
   576           Error Handling
   577         </h3>
   578         <dl class="domintro">
   579           <dt>
   580             <var title="">error</var> . <code title="dom-NavigatorNetworkServiceError-code"><a href=
   581             "#dom-navigatornetworkserviceerror-code">code</a></code>
   582           </dt>
   583           <dd>
   584             <p>
   585               Returns the current error's error code. At the current time, this will be <code>1</code> or
   586               <code>2</code>, for which the corresponding error constants <a href=
   587               "#dom-navigatornetworkserviceerror-permission_denied"><code>PERMISSION_DENIED_ERR</code></a> and <a href=
   588               "#dom-navigatornetworkserviceerror-unknown_type_prefix"><code>UNKNOWN_TYPE_PREFIX_ERR</code></a> are
   589               defined.
   590             </p>
   591           </dd>
   592         </dl>
   593         <p>
   594           The <dfn id="dom-navigatornetworkserviceerror-code"
   595              title="dom-navigatornetworkserviceerror-code"><code>code</code></dfn> attribute of a <a href=
   596              "#navigatornetworkserviceerror"><code>NavigatorNetworkServiceError</code></a> object <em class=
   597              "ct">MUST</em> return the code for the error, which will be one of the following:
   598         </p>
   599         <dl>
   600           <dt>
   601             <dfn id="dom-navigatornetworkserviceerror-permission_denied"
   602                 title="dom-navigatornetworkserviceerror-permission_denied"><code>PERMISSION_DENIED_ERR</code></dfn>
   603                 (numeric value 1)
   604           </dt>
   605           <dd>
   606             The user or user agent denied the page permission to access any services.
   607           </dd>
   608           <dt>
   609             <dfn id="dom-navigatornetworkserviceerror-unknown_type_prefix"
   610                 title="dom-navigatornetworkserviceerror-unknown_type_prefix"><code>UNKNOWN_TYPE_PREFIX_ERR</code></dfn>
   611                 (numeric value 2)
   612           </dt>
   613           <dd>
   614             No <a>valid service type</a> tokens were provided in the method invocation.
   615           </dd>
   616         </dl>
   617       </section>
   618     </section>
   619     <section>
   620       <h2>
   621         Obtaining networked services
   622       </h2>
   623       <p>
   624         The <a href="#networkservices"><code>NetworkServices</code></a> interface represents a collection of zero or
   625         more <dfn>indexed properties</dfn> that are each a <a>user-authorized</a> <a href=
   626         "#networkservice"><code>NetworkService</code></a> object.
   627       </p>
   628       <p>
   629         A <a href="#networkservices"><code>NetworkServices</code></a> object is the top level success callback
   630         parameter from a call to <a href="#dom-navigator-getnetworkservices"><code>getNetworkServices()</code></a>.
   631       </p>
   632       <pre class="widl">
   633 [NoInterfaceObject]
   634 interface <dfn id="networkservices">NetworkServices</dfn> {
   635   readonly attribute unsigned long    <a href="#dom-networkservices-length">length</a>;
   636   getter <a href="#networkservice">NetworkService</a> (unsigned long index);
   637   <a href="#networkservice">NetworkService</a>? <a href=
   638 "#dom-networkservices-getservicebyid">getServiceById</a>(DOMString id);
   639 
   640   readonly attribute unsigned long    <a href="#dom-networkservices-servicesavailable">servicesAvailable</a>;
   641 
   642   // event handler attributes
   643            attribute <a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#eventhandler"
   644      class="externalDFN">EventHandler</a>     <a href="#dom-networkservices-onserviceavailable">onserviceavailable</a>;
   645            attribute <a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#eventhandler"
   646      class="externalDFN">EventHandler</a>     <a href=
   647      "#dom-networkservices-onserviceunavailable">onserviceunavailable</a>;
   648 
   649 };
   650 
   651 <a href="#networkservices">NetworkServices</a> implements <a href=
   652 "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#interface-eventtarget"
   653      class="externalDFN">EventTarget</a>;
   654 </pre>
   655       <section>
   656         <h2>
   657           Attributes
   658         </h2>
   659         <dl class="domintro">
   660           <dt>
   661             <code title="dom-networkservices-length"><a href="#dom-networkservices-length">length</a></code>
   662           </dt>
   663           <dd>
   664             <p>
   665               Returns the current number of items in the current object's collection of <a href=
   666               "#networkservice"><code>NetworkService</code></a> objects.
   667             </p>
   668           </dd>
   669           <dt>
   670             <code title="dom-networkservices-servicesavailable"><a href=
   671             "#dom-networkservices-servicesavailable">servicesAvailable</a></code>
   672           </dt>
   673           <dd>
   674             <p>
   675               Returns the current number of items matching one of the app-requested <a>valid service type</a> tokens in
   676               the <a>list of available service records</a>.
   677             </p>
   678           </dd>
   679         </dl>
   680         <div>
   681           <p>
   682             The <dfn id="dom-networkservices-length"><code>length</code></dfn> attribute MUST return the number of
   683             <a href="#networkservice"><code>NetworkService</code></a> objects represented by the collection.
   684           </p>
   685           <p>
   686             The <dfn id="dom-networkservices-servicesavailable"><code>servicesAvailable</code></dfn> attribute MUST
   687             return the number of services in the <a>list of available service records</a> whose <code>type</code>
   688             attribute matches any of the <a>valid service type</a> tokens that was initially used to create the current
   689             <a href="#networkservices"><code>NetworkServices</code></a> object.
   690           </p>
   691         </div>
   692       </section>
   693       <section>
   694         <h2>
   695           Methods
   696         </h2>
   697         <dl class="domintro">
   698           <dt>
   699             <code title="networkservices-getter"><a href="#networkservices">services</a></code> [ <var title=
   700             "">index</var> ]
   701           </dt>
   702           <dd>
   703             <p>
   704               Returns the specified <a href="#networkservice"><code>NetworkService</code></a> object.
   705             </p>
   706           </dd>
   707           <dt>
   708             <code title="networkservices-getter"><a href="#networkservices">services</a></code> . <code title=
   709             "dom-networkservices-getservicebyid"><a href=
   710             "#dom-networkservices-getservicebyid">getServiceById</a></code> ( <var title="">id</var> )
   711           </dt>
   712           <dd>
   713             <p>
   714               Returns the <a href="#networkservice"><code>NetworkService</code></a> object with the given identifier,
   715               or null if no service has that identifier.
   716             </p>
   717           </dd>
   718         </dl>
   719         <p>
   720           A <a href="#networkservices"><code>NetworkServices</code></a> object represents the current collection of
   721           zero or more <a href="#networkservice"><code>NetworkService</code></a> objects - its <a>indexed
   722           properties</a>. A <a href="#networkservices"><code>NetworkServices</code></a> object is
   723           <span>immutable</span> meaning that <a>indexed properties</a> cannot be added and <a>indexed properties</a>
   724           cannot be removed for the lifetime of a <a href="#networkservices"><code>NetworkServices</code></a> object.
   725         </p>
   726         <p class="note">
   727           Each service in a <a href="#networkservices"><code>NetworkServices</code></a> object thus has an index; the
   728           first has the index 0, and each subsequent service is numbered one higher than the previous one.
   729         </p>
   730         <p>
   731           The <a href=
   732           "http://www.whatwg.org/specs/web-apps/current-work/multipage/infrastructure.html#supported-property-indices"
   733              class="externalDFN">supported property indices</a> of <a href=
   734              "#networkservices"><code>NetworkServices</code></a> objects at any instant are the numbers from zero to
   735              the number of the <a href="#networkservice"><code>NetworkService</code></a> objects in the collection
   736              minus one.
   737         </p>
   738         <p>
   739           To <a href=
   740           "http://www.whatwg.org/specs/web-apps/current-work/multipage/infrastructure.html#determine-the-value-of-an-indexed-property"
   741              class="externalDFN">determine the value of an indexed property</a> for a given index <var>index</var> in a
   742              <a href="#networkservices"><code>NetworkServices</code></a> object the user agent MUST return the <a href=
   743              "#networkservice"><code>NetworkService</code></a> object that represents the <var>index</var>th item in
   744              the collection.
   745         </p>
   746         <p>
   747           The <dfn id="dom-networkservices-getservicebyid"><code>getServiceById(id)</code></dfn> method <em class=
   748           "ct">MUST</em> return the first <a href="#networkservice"><code>NetworkService</code></a> object in the
   749           collection whose <a href="#dom-networkservice-id"><code>id</code></a> attribute is equal to the value of the
   750           <var>id</var> argument provided. When no <a href="#networkservice"><code>NetworkService</code></a> objects
   751           match the given argument, the method MUST return null.
   752         </p>
   753         <p>
   754           Services available within the local network can connect and disconnect at different times during the
   755           execution of a web page. A <a>user agent</a> can inform a web page when the state of networked services
   756           matching the requested <a>valid service type</a> change. Web pages can use this information to enable in-page
   757           experiences for communicating the state of networked services with the ability to change the particular
   758           service or set of services the page is connected to by re-invoking the <a href=
   759           "#dom-navigator-getnetworkservices"><code>getNetworkServices()</code></a> method.
   760         </p>
   761       </section>
   762       <section>
   763         <h2>
   764           Events
   765         </h2>
   766         <p>
   767           The following are the event handlers (and their corresponding event handler event types) that <em class=
   768           "ct">MUST</em> be supported, as IDL attributes, by all objects implementing the <a href=
   769           "#networkservices"><code>NetworkServices</code></a> interface:
   770         </p>
   771         <table border="1">
   772           <thead>
   773             <tr>
   774               <th>
   775                 <span title="event handlers">Event handler</span>
   776               </th>
   777               <th>
   778                 <span>Event handler event type</span>
   779               </th>
   780             </tr>
   781           </thead>
   782           <tbody>
   783             <tr>
   784               <td>
   785                 <dfn id="dom-networkservices-onserviceavailable"
   786                     title="dom-NetworkServices-onserviceavailable"><code>onserviceavailable</code></dfn>
   787               </td>
   788               <td>
   789                 <a href="#event-serviceavailable"><code>serviceavailable</code></a>
   790               </td>
   791             </tr>
   792             <tr>
   793               <td>
   794                 <dfn id="dom-networkservices-onserviceunavailable"
   795                     title="dom-NetworkServices-onserviceunavailable"><code>onserviceunavailable</code></dfn>
   796               </td>
   797               <td>
   798                 <a href="#event-serviceunavailable"><code>serviceunavailable</code></a>
   799               </td>
   800             </tr>
   801           </tbody>
   802         </table>
   803       </section>
   804     </section>
   805     <section>
   806       <h2>
   807         Communicating with a networked service
   808       </h2>
   809       <p>
   810         The <a href="#networkservice"><code>NetworkService</code></a> interface is used to provide a set of connection
   811         information for an HTTP service endpoint and if available, service events, running on a networked device.
   812       </p>
   813       <pre class="widl">
   814 [NoInterfaceObject]
   815 interface <dfn id="networkservice">NetworkService</dfn> {
   816   readonly attribute DOMString        <a href="#dom-networkservice-id">id</a>;
   817   readonly attribute DOMString        <a href="#dom-networkservice-name">name</a>;
   818   readonly attribute DOMString        <a href="#dom-networkservice-type">type</a>;
   819   readonly attribute DOMString        <a href="#dom-networkservice-url">url</a>;
   820   readonly attribute DOMString        <a href="#dom-networkservice-config">config</a>;
   821 
   822   readonly attribute boolean          <a href="#dom-networkservice-online">online</a>;
   823 
   824   // event handler attributes
   825            attribute <a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#eventhandler"
   826      class="externalDFN">EventHandler</a>     <a href="#dom-networkservice-onserviceonline">onserviceonline</a>;
   827            attribute <a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#eventhandler"
   828      class="externalDFN">EventHandler</a>     <a href="#dom-networkservice-onserviceoffline">onserviceoffline</a>;
   829 
   830            attribute <a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#eventhandler"
   831      class="externalDFN">EventHandler</a>     <a href="#dom-networkservice-onnotify">onnotify</a>;
   832 };
   833 
   834 <a href="#networkservice">NetworkService</a> implements <a href=
   835 "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#interface-eventtarget"
   836      class="externalDFN">EventTarget</a>;
   837 </pre>
   838       <section>
   839         <h2>
   840           Attributes
   841         </h2>
   842         <dl class="domintro">
   843           <dt>
   844             <var title="">service</var> . <code title="dom-networkservice-id"><a href=
   845             "#dom-networkservice-id">id</a></code>
   846           </dt>
   847           <dd>
   848             <p>
   849               A unique identifier for the given user-selected service instance.
   850             </p>
   851           </dd>
   852           <dt>
   853             <var title="">service</var> . <code title="dom-networkservice-name"><a href=
   854             "#dom-networkservice-name">name</a></code>
   855           </dt>
   856           <dd>
   857             <p>
   858               The name of the user-selected service.
   859             </p>
   860           </dd>
   861           <dt>
   862             <var title="">service</var> . <code title="dom-networkservice-type"><a href=
   863             "#dom-networkservice-type">type</a></code>
   864           </dt>
   865           <dd>
   866             <p>
   867               The <a>valid service type</a> token value of the user-selected service.
   868             </p>
   869           </dd>
   870           <dt>
   871             <var title="">service</var> . <code title="dom-networkservice-url"><a href=
   872             "#dom-networkservice-url">url</a></code>
   873           </dt>
   874           <dd>
   875             <p>
   876               The control URL endpoint (including any required port information) of the user-selected control service
   877               that has been added to the <a>entry script origin's URL whitelist</a>.
   878             </p>
   879           </dd>
   880           <dt>
   881             <var title="">service</var> . <code title="dom-networkservice-config"><a href=
   882             "#dom-networkservice-config">config</a></code>
   883           </dt>
   884           <dd>
   885             <p>
   886               The configuration information associated with the service depending on the requested service type.
   887             </p>
   888           </dd>
   889         </dl>
   890         <p>
   891           The <dfn id="dom-networkservice-id"><code>id</code></dfn> attribute is a unique identifier for the service.
   892           The same service provided at different times or on different objects MUST have the same <a href=
   893           "#dom-networkservice-id"><code>id</code></a> value.
   894         </p>
   895         <p>
   896           The <dfn id="dom-networkservice-name"><code>name</code></dfn> attribute represents a human-readable title for
   897           the service.
   898         </p>
   899         <p>
   900           The <dfn id="dom-networkservice-type"><code>type</code></dfn> attribute reflects the value of the <a>valid
   901           service type</a> of the service.
   902         </p>
   903         <p>
   904           The <dfn id="dom-networkservice-url"><code>url</code></dfn> attribute is an <a href=
   905           "http://www.w3.org/TR/html5/urls.html#absolute-url"
   906              class="externalDFN">absolute URL</a> pointing to the root HTTP endpoint for the service that has been
   907              added to the <a>entry script origin's URL whitelist</a>. Web pages can subsequently use this value for
   908              implicit cross-document messaging via various existing mechanisms (e.g. Web Sockets, Server-Sent Events,
   909              Web Messaging, XMLHttpRequest).
   910         </p>
   911         <p>
   912           The <dfn id="dom-networkservice-config"><code>config</code></dfn> attribute provides the raw configuration
   913           information extracted from the given network service.
   914         </p>
   915       </section>
   916       <section>
   917         <h3>
   918           States
   919         </h3>
   920         <dl class="domintro">
   921           <dt>
   922             <var title="">service</var> . <code title="dom-networkservice-online"><a href=
   923             "#dom-networkservice-online">online</a></code>
   924           </dt>
   925           <dd>
   926             <p>
   927               Returns <code>true</code> if the service is reporting that it is accessible on the local network or
   928               <code>false</code> if the service is reporting that it is no longer accessible (temporarily or
   929               permanently) on the local network.
   930             </p>
   931           </dd>
   932         </dl>
   933         <p>
   934           The <dfn id="dom-networkservice-online"><code>online</code></dfn> attribute indicates whether the service is
   935           reporting itself as being either <var>online</var>, and therefore accessible on the local network, in which
   936           case this attribute will return <code>true</code> or, <var>offline</var>, and therefore not accessible on the
   937           local network, either temporarily or permanently, in which case this attribute will return
   938           <code>false</code>. This attribute MUST default to <code>true</code>.
   939         </p>
   940       </section>
   941       <section>
   942         <h3>
   943           Events
   944         </h3>
   945         <p>
   946           The following are the event handlers (and their corresponding event handler event types) that <em class=
   947           "ct">MUST</em> be supported, as IDL attributes, by all objects implementing the <a href=
   948           "#networkservice"><code>NetworkService</code></a> interface:
   949         </p>
   950         <table border="1">
   951           <thead>
   952             <tr>
   953               <th>
   954                 <span title="event handlers">Event handler</span>
   955               </th>
   956               <th>
   957                 <span>Event handler event type</span>
   958               </th>
   959             </tr>
   960           </thead>
   961           <tbody>
   962             <tr>
   963               <td>
   964                 <dfn id="dom-networkservice-onnotify"
   965                     title="dom-NetworkService-onnotify"><code>onnotify</code></dfn>
   966               </td>
   967               <td>
   968                 <a href="#event-notify"><code>notify</code></a>
   969               </td>
   970             </tr>
   971             <tr>
   972               <td>
   973                 <dfn id="dom-networkservice-onserviceonline"
   974                     title="dom-NetworkService-onserviceonline"><code>onserviceonline</code></dfn>
   975               </td>
   976               <td>
   977                 <a href="#event-serviceonline"><code>serviceonline</code></a>
   978               </td>
   979             </tr>
   980             <tr>
   981               <td>
   982                 <dfn id="dom-networkservice-onserviceoffline"
   983                     title="dom-NetworkService-onserviceoffline"><code>onserviceoffline</code></dfn>
   984               </td>
   985               <td>
   986                 <a href="#event-serviceoffline"><code>serviceoffline</code></a>
   987               </td>
   988             </tr>
   989           </tbody>
   990         </table>
   991       </section>
   992     </section>
   993     <section>
   994       <h2>
   995         Service Discovery
   996       </h2>
   997       <p>
   998         A <a>user agent</a> conforming to this specification MAY implement <abbr title=
   999         "Simple Service Discovery Protocol">SSDP</abbr> [[!UPNP-DEVICEARCH11]], Zeroconf [[!DNS-SD]] + [[!MDNS]] and/or
  1000         <abbr title="Discovery and Launch Protocol">DIAL</abbr> [<a href=
  1001         "https://sites.google.com/a/dial-multiscreen.org/dial/dial-protocol-specification">DIAL</a>] <dfn>service
  1002         discovery mechanisms</dfn> - the requirements detailed in this section of the specification - to enable Web
  1003         pages to request and connect with HTTP services running on networked devices, discovered via any of these
  1004         mechanisms, through this API. When a <a>user agent</a> implements any of these <a>service discovery
  1005         mechanisms</a>, then it MUST conform to the corresponding algorithms provided in this section of the
  1006         specification.
  1007       </p>
  1008       <p>
  1009         This section presents how the results of these <a>service discovery mechanisms</a> will be matched to requested
  1010         service types, how the user agent stores available and active services and how their properties are applied to
  1011         any resulting <a href="#networkservice"><code>NetworkService</code></a> objects.
  1012       </p>
  1013       <p>
  1014         It is expected that user agents will perform these <a>service discovery mechanisms</a> asynchronously and
  1015         periodically update the <a>list of available service records</a> as required. The timing of any <a>service
  1016         discovery mechanisms</a> is an implementation detail left to the discretion of the implementer (e.g. by
  1017         continuously monitoring the network as a background process or on invocation of this API from a Web page).
  1018       </p>
  1019       <p>
  1020         The <dfn>list of available service records</dfn> is a single dynamic internal lookup table within user agents
  1021         that is used to track all the services that have been discovered and are available in the current network at
  1022         the current time. At any point during the running of either of the two <a>service discovery mechanisms</a> then
  1023         existing entries within this table can be updated, entries can be added and entries can be removed as the
  1024         status of networked services changes according to the rules defined in this specification.
  1025       </p>
  1026       <p>
  1027         The <dfn>list of active service managers</dfn> is an internal list within user agents that is used to track all
  1028         <a href="#networkservices"><code>NetworkServices</code></a> objects currently being shared with any web pages
  1029         at the current time within the user agent. Each <a href="#networkservices"><code>NetworkServices</code></a>
  1030         object in the <a>list of active service managers</a> represents a collection of zero or more <a href=
  1031         "#networkservice"><code>NetworkService</code></a> objects - known as its <dfn>indexed properties</dfn>.
  1032         <a href="#networkservice"><code>NetworkService</code></a> objects are attached as the <a>indexed properties</a>
  1033         of a <a href="#networkservices"><code>NetworkServices</code></a> object as part of the <a href=
  1034         "#dom-navigator-getnetworkservices"><code>getNetworkServices()</code></a> algorithm.
  1035       </p>
  1036       <p>
  1037         The rule for <dfn>adding an available service</dfn> is the process of adding a <a>new service</a> or updating
  1038         an <a>existing service</a> that is generally available on the user's current network in the <a>list of
  1039         available service records</a>. This rule takes one argument, <var>network service record</var>, and consists of
  1040         running the following steps:
  1041       </p>
  1042       <ol class="rule">
  1043         <li>For each <var>existing service record</var> in the current <a>list of available service records</a>, run
  1044         the following sub-steps:
  1045           <ol class="rule">
  1046             <li>If the <var>existing service record</var>'s <code>id</code> property does not equal <var>network
  1047             service record</var>'s <code>id</code> property then abort any remaining sub-steps and continue at the next
  1048             available <var>existing service record</var>.
  1049             </li>
  1050             <li>Replace the value of <var>existing service record</var> in the current <a>list of available service
  1051             records</a> with the value of <var>network service record</var>, aborting any remaining steps in this
  1052             algorithm and return.
  1053             </li>
  1054           </ol>
  1055         </li>
  1056         <li>Add <var>network service record</var> to the <a>list of available service records</a> as a new item.
  1057         </li>
  1058         <li>For each <var>service manager</var> in the <a>list of active service managers</a> run the following steps:
  1059           <ol class="rule">
  1060             <li>For each <var>active service</var> in <var>service manager</var> run the following steps:
  1061               <ol class="rule">
  1062                 <li>If the <var>network service record</var>'s <code>id</code> property equals the <var>active
  1063                 service</var>'s <code>id</code> attribute then set <var>active service</var>'s <a href=
  1064                 "#dom-networkservice-online"><code>online</code></a> attribute to <code>true</code> and then <a href=
  1065                 "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
  1066                       class="externalDFN">queue a task</a> to dispatch a newly created event with the name <a href=
  1067                       "#event-serviceonline"><code>serviceonline</code></a> that uses the <a href=
  1068                       "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1069                       class="externalDFN"><code>Event</code></a> interface, which does not bubble, is not cancellable,
  1070                       and has no default action, at the current <var>active service</var> object.
  1071                 </li>
  1072               </ol>
  1073             </li>
  1074             <li>Let <var>'service type in current service manager' flag</var> be <code>false</code>.
  1075             </li>
  1076             <li>For each <var>requested control type</var> of the <var>requested control types</var> in <var>service
  1077             manager</var> run the following steps:
  1078               <ol class="rule">
  1079                 <li>If <var>network service record</var>'s <code>type</code> property does not equal <var>requested
  1080                 control type</var> then abort any remaining sub-steps and continue at the next available <var>requested
  1081                 control type</var>.
  1082                 </li>
  1083                 <li>Set the <var>'service type in current service manager' flag</var> to <code>true</code>, abort any
  1084                 remaining sub-steps and continue.
  1085                 </li>
  1086               </ol>
  1087             </li>
  1088             <li>If the <var>'service type in current service manager' flag</var> is set to <code>true</code> then
  1089             increment <var>service manager</var>'s <a href=
  1090             "#dom-networkservices-servicesavailable"><code>servicesAvailable</code></a> attribute by <code>1</code> and
  1091             then <a href="http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
  1092                   class="externalDFN">queue a task</a> to dispatch a newly created event with the name <a href=
  1093                   "#event-serviceavailable"><code>serviceavailable</code></a> that uses the <a href=
  1094                   "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1095                   class="externalDFN"><code>Event</code></a> interface, which does not bubble, is not cancellable, and
  1096                   has no default action, at the current <var>service manager</var> object.
  1097             </li>
  1098           </ol>
  1099         </li>
  1100       </ol>
  1101       <p>
  1102         The rule for <dfn>removing an available service</dfn> is the general process of removing an <a>existing
  1103         service</a> from the <a>list of available service records</a> that has left the user's current network or has
  1104         otherwise expired. This rule takes one argument, <var>service identifier</var>, and consists of running the
  1105         following steps:
  1106       </p>
  1107       <ol class="rule">
  1108         <li>For each <var>existing service record</var> in the current <a>list of available service records</a>, run
  1109         the following sub-steps:
  1110           <ol class="rule">
  1111             <li>If the <var>existing service record</var>'s <code>id</code> property does not match <var>service
  1112             identifier</var> then skip any remaining sub-steps for the current <var>existing service record</var> and
  1113             continue at the next available <var>existing service record</var>.
  1114             </li>
  1115             <li>Let <var>'service type in use' flag</var> be <code>false</code>.
  1116             </li>
  1117             <li>For each <var>service manager</var> in the <a>list of active service managers</a> run the following
  1118             steps:
  1119               <ol class="rule">
  1120                 <li>Let <var>'service type in current service manager' flag</var> be <code>false</code>.
  1121                 </li>
  1122                 <li>For each <var>active service</var> in <var>service manager</var> run the following steps:
  1123                   <ol class="rule">
  1124                     <li>If <var>existing service record</var>'s <code>id</code> property equals the <var>active
  1125                     service</var>'s <code>id</code> attribute and <var>active service</var>'s <a href=
  1126                     "#dom-networkservice-online"><code>online</code></a> attribute is currently set to
  1127                     <code>true</code> then set <var>active service</var>'s <a href="#dom-networkservice-online"><code>
  1128                       online</code></a> attribute to <code>false</code> and then <a href=
  1129                       "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
  1130                           class="externalDFN">queue a task</a> to dispatch a newly created event with the name <a href=
  1131                           "#event-serviceoffline"><code>serviceoffline</code></a> that uses the <a href=
  1132                           "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1133                           class="externalDFN"><code>Event</code></a> interface, which does not bubble, is not
  1134                           cancellable, and has no default action, at the current <var>active service</var>.
  1135                     </li>
  1136                   </ol>
  1137                 </li>
  1138                 <li>For each <var>requested control type</var> of the <var>requested control types</var> in
  1139                 <var>service manager</var> run the following steps:
  1140                   <ol class="rule">
  1141                     <li>If <var>existing service record</var>'s <code>type</code> property does not equal
  1142                     <var>requested control type</var> then abort any remaining sub-steps and continue at the next
  1143                     available <var>requested control type</var>.
  1144                     </li>
  1145                     <li>Set the <var>'service type in current service manager' flag</var> to <code>true</code> and the
  1146                     <var>'service type in use' flag</var> to <code>true</code>, abort any remaining sub-steps and
  1147                     continue.
  1148                     </li>
  1149                   </ol>
  1150                 </li>
  1151                 <li>If the <var>'service type in current service manager' flag</var> is set to <code>true</code> then
  1152                 decrement <var>service manager</var>'s <a href=
  1153                 "#dom-networkservices-servicesavailable"><code>servicesAvailable</code></a> attribute by <code>1</code>
  1154                 and then <a href=
  1155                 "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
  1156                       class="externalDFN">queue a task</a> to dispatch a newly created event with the name <a href=
  1157                       "#event-serviceunavailable"><code>serviceunavailable</code></a> that uses the <a href=
  1158                       "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1159                       class="externalDFN"><code>Event</code></a> interface, which does not bubble, is not cancellable,
  1160                       and has no default action, at the current <var>service manager</var> object.
  1161                 </li>
  1162               </ol>
  1163             </li>
  1164             <li>If the <var>'service type in use' flag</var> is <code>false</code> and the <var>existing service
  1165             record</var>'s <code>type</code> property begins with the DOMString "<code>upnp:</code>" and <var>existing
  1166             service record</var>'s <code>eventsURL</code> property is set then run the rule to <a>terminate an existing
  1167             UPnP Events Subscription</a>, if one is currently active (as a result of having previously called <a>setup
  1168             a UPnP Events Subscription</a> against the current <var>existing service record</var>).
  1169             </li>
  1170             <li>Remove <var>existing service record</var> from the current <a>list of available service records</a>.
  1171             </li>
  1172           </ol>
  1173         </li>
  1174       </ol>
  1175       <p>
  1176         User agents SHOULD expire a service record from the <a>list of available service records</a> when its
  1177         <code>expiryTimestamp</code> attribute exceeds the current UTC timestamp. When this condition is met the
  1178         <a>user agent</a> SHOULD run the rule for <a>removing an available service</a>, passing in the expired service
  1179         record's <code>id</code> attribute as the only argument.
  1180       </p>
  1181       <section>
  1182         <h4>
  1183           Zeroconf (<abbr title="Multicast DNS">mDNS</abbr> + <abbr title="Domain Name System">DNS</abbr>-<abbr title=
  1184           "Service Discovery">SD</abbr>)
  1185         </h4>
  1186         <p>
  1187           For each DNS response received from a user-agent-initiated Multicast DNS Browse for <abbr title=
  1188           "DNS Pointer Record">PTR</abbr> records with the name <code>_services._dns-sd._udp</code> on the resolved
  1189           recommended automatic browsing domain [[!MDNS]], the <a>user agent</a> MUST run the following steps:
  1190         </p>
  1191         <ol class="rule">
  1192           <li>Let <var>service mDNS responses</var> be an array of PTR records received by issuing a Multicast DNS
  1193           Browse for PTR records with the name of the current discovered service type.
  1194           </li>
  1195           <li>For each Object <var>service mDNS response</var> in <var>service mDNS responses</var>, run the following
  1196           steps:
  1197             <ol>
  1198               <li>Let <var>network service record</var> be an Object consisting of the following empty properties:
  1199               <code>id</code>, <code>name</code>, <code>type</code>, <code>url</code>, <code>config</code>,
  1200               <code>expiryTimestamp</code>.
  1201               </li>
  1202               <li>Set <var>network service record</var>'s <code>id</code> property to the value of the full PTR Service
  1203               Instance Name [[!MDNS]].
  1204               </li>
  1205               <li>Set <var>network service record</var>'s <code>name</code> property to the value of the PTR Service
  1206               Instance Name's <var>Instance</var> component [[!MDNS]].
  1207               </li>
  1208               <li>Set <var>network service record</var>'s <code>type</code> property to the concatenation of the string
  1209               <code>zeroconf:</code> followed be the value of the PTR Service Instance Name's <var>Service</var>
  1210               component [[!MDNS]].
  1211               </li>
  1212               <li>Set <var>network service record</var>'s <code>url</code> property to the resolvable Service URL
  1213               obtained from performing an DNS-SD Lookup [[!DNS-SD]] of the current service from the PTR record provided
  1214               [[!MDNS]].
  1215               </li>
  1216               <li>Set <var>network service record</var>'s <code>config</code> property to the string value of the
  1217               contents of the first DNS-SD TXT record associated with the <var>service mDNS response</var> as defined
  1218               in [[!DNS-SD]].
  1219               </li>
  1220               <li>Set <var>network service record</var>'s <code>expiryTimestamp</code> property to the value of the
  1221               current date, in UTC timestamp format, plus a value of <code>120</code> seconds.
  1222               </li>
  1223               <li>Run the general rule for <a>adding an available service</a>, passing in the current <var>network
  1224               service record</var> as the only argument.
  1225               </li>
  1226             </ol>
  1227           </li>
  1228         </ol>
  1229       </section>
  1230       <section>
  1231         <h5>
  1232           Simple Service Discovery Protocol (<abbr title="Simple Service Discovery Protocol">SSDP</abbr>)
  1233         </h5>
  1234         <p>
  1235           A user agent that implements UPnP service discovery MUST issue a <dfn>search request for UPnP root
  1236           devices</dfn> against the user's current local network according to the full normative text and timing
  1237           provided in 'Section 1.3.2: Search request with M-SEARCH' detailed in [[!UPNP-DEVICEARCH11]].
  1238         </p>
  1239         <p>
  1240           The user agent MUST issue all <a title="search request for UPnP root devices">search requests for UPnP root
  1241           devices</a> with a HTTP request line equal to <code>M-SEARCH * HTTP/1.1</code>, with a HOST header equal to
  1242           the reserved multicast address and port of <code>239.255.255.250:1900</code> and a MAN header equal to
  1243           <code>ssdp:discover</code>. The <a>user agent</a> must also send an ST header with this HTTP request equal to
  1244           the String value of <code>ssdp:all</code> or <code>upnp:rootdevice</code> or a single <a>valid service
  1245           type</a> token. The user-agent MUST also send an MX header equal to a <dfn>maximum UPnP advertisement
  1246           response wait time</dfn> value between <code>1</code> and <code>5</code> seconds with this HTTP request.
  1247         </p>
  1248         <p>
  1249           The user agent MUST listen for any incoming responses to any <a>search request for UPnP root devices</a>.
  1250         </p>
  1251         <p>
  1252           For each <dfn>HTTP Response</dfn> following an initial <a>search request for UPnP root devices</a> sent on a
  1253           <a>standard UPnP address and port</a> the user agent MUST run the following steps:
  1254         </p>
  1255         <ol class="rule">
  1256           <li>If the <a>HTTP Response</a> is not a HTTP 200 OK response then this response is invalid and the user
  1257           agent MUST discard this response, abort any remaining steps and return. The user agent MAY issue a new
  1258           <a>search request for UPnP root devices</a> as a result of this error occurring.
  1259           </li>
  1260           <li>If the <a>maximum UPnP advertisement response wait time</a> has been exceeded since the initial <a>search
  1261           request for UPnP root devices</a> was sent then the <a>HTTP Response</a> is invalid and the user agent MUST
  1262           discard this response, abort any remaining steps and return. The user agent MAY stop listening for responses
  1263           from the current <a>search request for UPnP root devices</a> as a result of this error occurring. Equally,
  1264           the user agent MAY issue a new <a>search request for UPnP root devices</a> as a result of this error
  1265           occurring.
  1266           </li>
  1267           <li>Let <var>ssdp device</var> be an Object with a property for each HTTP header received in the <a>HTTP
  1268           Response</a>, with each key being the name of a HTTP response header and each value being that HTTP response
  1269           header's value.
  1270           </li>
  1271           <li>If <var>ssdp device</var> does not contain at least one <var>CACHE-CONTROL</var> entry, at least one
  1272           <var>USN</var> entry, at least one <var>ST</var> entry and at least one <var>LOCATION</var> entry then the
  1273           <a>HTTP Response</a> is invalid and the <a>user agent</a> MUST discard this response, abort any remaining
  1274           steps and return.
  1275           </li>
  1276           <li>The user agent MUST run the rule for <a>obtaining a UPnP Device Description File</a> passing in the first
  1277           occurrence of <var>LOCATION</var> from <var>ssdp device</var> as the <var>device descriptor URL</var>
  1278           argument and the first occurrence of <var>USN</var> from <var>ssdp device</var> as the <var>device
  1279           identifier</var> argument and the first occurrence of <var>CACHE-CONTROL</var> from <var>ssdp device</var>
  1280           (minus the leading string of <code>max-age=</code>) as the <var>device expiry</var> argument.
  1281           </li>
  1282         </ol>
  1283         <p>
  1284           The user agent MUST listen for incoming requests on the <dfn>standard UPnP address and port</dfn> on all
  1285           current local network interface addresses with the port <code>1900</code>.
  1286         </p>
  1287         <p>
  1288           For each <dfn>HTTP Request</dfn> received on a <a>standard UPnP address and port</a> the user agent MUST run
  1289           the following steps:
  1290         </p>
  1291         <ol class="rule">
  1292           <li>If the <a>HTTP Request</a> is not a HTTP NOTIFY request then it is not a valid UPnP Request and the user
  1293           agent MUST discard this request, abort any remaining steps and return.
  1294           </li>
  1295           <li>Let <var>ssdp device</var> be an Object with a property for each HTTP header received in the <a>HTTP
  1296           Request</a>, with each key being the name of a HTTP header and each value being that HTTP header's value.
  1297           </li>
  1298           <li>If <var>ssdp device</var>'s <var>NTS</var> entry is equal to <code>ssdp:alive</code> and the <a>HTTP
  1299           Request</a> does not contain at least one <var>CACHE-CONTROL</var> entry, at least one <var>USN</var> entry,
  1300           at least one <var>NT</var> entry, at least one <var>NTS</var> entry and at least one <var>LOCATION</var>
  1301           entry, then the <a>user agent</a> MUST discard this request, abort any remaining steps and return.
  1302           </li>
  1303           <li>If <var>ssdp device</var>'s <var>NTS</var> entry is equal to <code>ssdp:alive</code> then the user agent
  1304           MUST run the rule for <a>obtaining a UPnP Device Description File</a> passing in the first occurrence of
  1305           <var>LOCATION</var> from <var>ssdp device</var> as the <var>device descriptor URL</var> argument and the
  1306           first occurrence of <var>USN</var> from <var>ssdp device</var> as the <var>device identifier</var> argument
  1307           and the first occurrence of <var>CACHE-CONTROL</var> from <var>ssdp device</var> (minus the leading string of
  1308           <code>max-age=</code>) as the <var>device expiry</var>.<br>
  1309             <br>
  1310             Otherwise, if <var>ssdp device</var>'s <var>NTS</var> entry is equal to <code>ssdp:byebye</code> then the
  1311             user agent MUST run the rule for <a>removing all services from a registered UPnP Device</a> passing in the
  1312             first occurrence of <var>USN</var> from <var>ssdp device</var> as the <var>device identifier</var>
  1313             argument.
  1314           </li>
  1315         </ol>
  1316         <p>
  1317           The rule for <dfn>obtaining a UPnP Device Description File</dfn> is the process of obtaining the contents of
  1318           a standard UPnP Device Description [[!UPNP-DEVICEARCH11]] from a URL-based resource. This rule takes three
  1319           arguments - <var>device descriptor URL</var>, <var>device identifier</var> and <var>device expiry</var> - and
  1320           when called the user agent MUST run the following steps:
  1321         </p>
  1322         <ol class="rule">
  1323           <li>Let <var>device descriptor file</var> contain the contents of the file located at the URL provided in
  1324           <var>device descriptor URL</var> obtained according to the rules defined in 'Section 2.11: Retrieving a
  1325           description using HTTP' in [[!UPNP-DEVICEARCH11]].
  1326           </li>
  1327           <li>If the value provided in <var>device descriptor URL</var> cannot be resolved as a reachable URL on the
  1328           current network or the <var>device descriptor file</var> remains empty then it is invalid and the <a>user
  1329           agent</a> MUST abort any remaining steps and return.
  1330           </li>
  1331           <li>Run the rule for <a>processing a UPnP Device Description File</a>, passing in the current <var>device
  1332           descriptor file</var>, <var>device identifier</var> and <var>device expiry</var> arguments.
  1333           </li>
  1334         </ol>
  1335         <p>
  1336           The rule for <dfn>processing a UPnP Device Description File</dfn> is the process of parsing the contents of a
  1337           standard UPnP Device Description [[!UPNP-DEVICEARCH11]] and registering the UPnP services contained therein
  1338           within the <a>list of available service records</a>.
  1339         </p>
  1340         <p>
  1341           The rule for <a>processing a UPnP Device Description File</a> takes three arguments - <var>device descriptor
  1342           file</var>, <var>device identifier</var> and <var>device expiry</var> - and when called the user agent MUST
  1343           run the following steps:
  1344         </p>
  1345         <ol class="rule">
  1346           <li>Let <var>advertised services</var> be a list of all advertised services obtained from the <var>device
  1347           descriptor file</var> containing the value of the first occurrence of the <code>&lt;serviceList&gt;</code>
  1348           element as it is defined in 'Section 2.3: Device Description' in [[!UPNP-DEVICEARCH11]].
  1349           </li>
  1350           <li>For each <code>&lt;service&gt;</code> element - known as an <var>advertised service</var> - in
  1351           <var>advertised services</var> run the following steps:
  1352             <ol class="rule">
  1353               <li>Let <var>network service record</var> be a new Object consisting of the following empty properties:
  1354               <code>id</code>, <code>deviceId</code>, <code>name</code>, <code>type</code>, <code>url</code>,
  1355               <code>eventsUrl</code>, <code>config</code>, <code>expiryTimestamp</code>.
  1356               </li>
  1357               <li>Set <var>network service record</var>'s <code>id</code> property to the concatenated string value of
  1358               the first occurrence of the <code>&lt;UDN&gt;</code> element in the <var>device descriptor file</var>
  1359               with the <var>advertised service</var>'s <code>&lt;serviceId&gt;</code> sub-element.
  1360               </li>
  1361               <li>Set <var>network service record</var>'s <code>deviceId</code> property to the value of <var>device
  1362               identifier</var>.
  1363               </li>
  1364               <li>Set <var>network service record</var>'s <code>name</code> property to the string value of the first
  1365               occurrence of the <var>advertised service</var>'s <code>&lt;serviceId&gt;</code> sub-element.
  1366               </li>
  1367               <li>Set <var>network service record</var>'s <code>type</code> property to the concatenation of the string
  1368               <code>upnp:</code> followed by the string value of the first occurrence of the <var>advertised
  1369               service</var>'s <code>&lt;serviceType&gt;</code> sub-element.
  1370               </li>
  1371               <li>Set <var>network service record</var>'s <code>url</code> property to the string value of the first
  1372               occurrence of the <var>advertised service</var>'s <code>&lt;controlURL&gt;</code> sub-element.
  1373               </li>
  1374               <li>Set <var>network service record</var>'s <code>config</code> property to the string value of the
  1375               contents of the first occurrence of the <code>&lt;device&gt;</code> element in the <var>device descriptor
  1376               file</var>.
  1377               </li>
  1378               <li>If <var>advertised service</var>'s <code>&lt;eventSubURL&gt;</code> sub-element is not empty, then
  1379               set <var>network service record</var>'s <code>eventsUrl</code> property to the string value of the first
  1380               occurrence of the <var>advertised service</var>'s <code>&lt;eventSubURL&gt;</code> sub-element.
  1381               Otherwise, do not set <var>network service record</var>'s <code>eventsUrl</code> property.
  1382               </li>
  1383               <li>Set <var>network service record</var>'s <code>expiryTimestamp</code> property to the value of the
  1384               current date, in UTC timestamp format, plus the value of <var>device expiry</var>.
  1385               </li>
  1386               <li>Run the general rule for <a>adding an available service</a>, passing in the current <var>network
  1387               service record</var> as the only argument.
  1388               </li>
  1389             </ol>
  1390           </li>
  1391           <li>If <var>device descriptor file</var> contains a <code>&lt;deviceList&gt;</code> element then for each
  1392           <code>&lt;device&gt;</code> element within <code>&lt;deviceList&gt;</code> - herein known as an <var>embedded
  1393           device descriptor file</var> - the user agent MUST run the rule for <a>processing a UPnP Device Description
  1394           File</a>, passing in the current <var>embedded device descriptor file</var> as the <var>device descriptor
  1395           file</var> argument, along with the current <var>device identifier</var> and <var>device expiry</var>
  1396           arguments.
  1397           </li>
  1398         </ol>
  1399         <p>
  1400           The rule for <dfn>removing all services from a registered UPnP Device</dfn> is the process of removing all
  1401           services associated with a device from the <a>list of available service records</a> that has left the user's
  1402           current network or has otherwise timed out or expired. This rule takes one argument, <var>device
  1403           identifier</var>, and consists of running the following steps:
  1404         </p>
  1405         <ol class="rule">
  1406           <li>For each <var>existing service record</var> in the current <a>list of available service records</a>, run
  1407           the following sub-steps:
  1408             <ol class="rule">
  1409               <li>If the <var>existing service record</var>'s <code>deviceId</code> property does not match <var>device
  1410               identifier</var> then skip any remaining sub-steps for the current <var>existing service record</var> and
  1411               continue at the next available <var>existing service record</var>.
  1412               </li>
  1413               <li>Run the general rule for <a>removing an available service</a> passing in <var>existing service
  1414               record</var>'s <code>id</code> property as the only argument.
  1415               </li>
  1416             </ol>
  1417           </li>
  1418         </ol>
  1419         <p>
  1420           When the <a>user agent</a> is to <dfn>setup a UPnP Events Subscription</dfn>, it is to run the following
  1421           steps with the current <var>network service record</var> object as defined in 'Section 4.1.2: SUBSCRIBE with
  1422           NT and CALLBACK' in [[!UPNP-DEVICEARCH11]]:
  1423         </p>
  1424         <ol class="rule">
  1425           <li>If <var>network service record</var>'s <code>eventsUrl</code> property is empty then the <a>user
  1426           agent</a> MUST abort these steps.
  1427           </li>
  1428           <li>Let <var>callback URL</var> be the value of creating a new <a>user-agent generated callback url</a>.
  1429           </li>
  1430           <li>Send a HTTP SUBSCRIBE request with a <em>NT</em> header with a string value of <code>upnp:event</code>, a
  1431           <em>TIMEOUT</em> header with a user-agent defined timeout value (in the form <code>Second-XX</code> where
  1432           <code>XX</code> is the user-agent defined timeout value in seconds) and a <em>CALLBACK</em> header with a
  1433           string value of <var>callback URL</var> towards the <var>network service record</var>'s
  1434           <code>eventsUrl</code> property.
  1435           </li>
  1436           <li>If a non-200 OK response is received from the HTTP SUBSCRIBE request then the <a>user agent</a> MUST
  1437           abort these steps.
  1438           </li>
  1439           <li>On receiving a valid 200 OK response, run the following steps:
  1440             <ol class="rule">
  1441               <li>Let <var>callback ID</var> equal the string value of the first included <em>SID</em> header, if it
  1442               exists.
  1443               </li>
  1444               <li>Let <var>timeout date</var> equal the sum of the current UTC date value plus the integer value of the
  1445               first included <em>TIMEOUT</em> header (minus the leading string of <code>Second-</code>), if it exists.
  1446               </li>
  1447               <li>Run the following steps asynchronously and continue to the step labeled <em>listen</em> below.
  1448               </li>
  1449               <li>
  1450                 <em>Refresh Subscription</em>: Run the following steps at a set interval (X) within the <a>user
  1451                 agent</a>:
  1452                 <ol class="rule">
  1453                   <li>Let <var>current date</var> equal the current UTC date.
  1454                   </li>
  1455                   <li>If <var>current date</var> is less than the <var>timeout date</var> then continue to the step
  1456                   labeled <em>refresh subscription</em> above.
  1457                   </li>
  1458                   <li>Send a HTTP SUBSCRIBE request with a <em>SID</em> header with the string value of <var>callback
  1459                   ID</var> and a user-agent defined <em>TIMEOUT</em> header (in the form <code>Second-XX</code> where
  1460                   <code>XX</code> is the user-agent defined timeout value in seconds) towards the <var>network service
  1461                   record</var>'s <code>eventsUrl</code> property.
  1462                   </li>
  1463                   <li>On receiving a valid 200 OK, update <var>callback ID</var> with the string value of the first
  1464                   included <em>SID</em> header and set <var>timeout date</var> to the sum of the current UTC date value
  1465                   plus the integer value of the first included <em>TIMEOUT</em> header (minus the leading string of
  1466                   <code>Second-</code>), if it exists. If the current date is greater than or equal to <var>timeout
  1467                   date</var> then the <a>user agent</a> SHOULD continue from the step labeled <em>refresh
  1468                   subscription</em> above. For all non 200 OK responses the <a>user agent</a> SHOULD continue from the
  1469                   step labeled <em>refresh subscription</em> above.
  1470                   </li>
  1471                 </ol>
  1472               </li>
  1473               <li>
  1474                 <em>Listen</em>: For each HTTP NOTIFY request received at the <var>callback URL</var> the <a>user
  1475                 agent</a> is to run the following steps:
  1476                 <ol class="rule">
  1477                   <li>Let <var>content clone</var> be the result of obtaining the message body of the HTTP NOTIFY
  1478                   request. If <var>content clone</var> is empty, then the <a>user agent</a> MUST abort these steps.
  1479                   </li>
  1480                   <li>Let <var>notification event</var> be a new simple event that uses the <a href=
  1481                   "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1482                         class="externalDFN"><code>Event</code></a> interface with the name <a href=
  1483                         "#event-notify"><code>notify</code></a>, which does not bubble, is not cancellable, and has no
  1484                         default action.
  1485                   </li>
  1486                   <li>Let the <code>data</code> attribute of <var>notification event</var> have the DOMString value of
  1487                   <var>content clone</var>.
  1488                   </li>
  1489                   <li>
  1490                     <a href="http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
  1491                         class="externalDFN">Queue a task</a> to dispatch <var>notification event</var> at the current
  1492                         <a><code>NetworkService</code></a> object.
  1493                   </li>
  1494                   <li>Return a HTTP 200 OK response to the sender of the HTTP NOTIFY request.
  1495                   </li>
  1496                 </ol>
  1497               </li>
  1498             </ol>
  1499           </li>
  1500         </ol>
  1501         <p>
  1502           A <a>user agent</a> can <dfn>terminate an existing UPnP Events Subscription</dfn> at any time for a
  1503           <var>network service record</var> by sending an HTTP UNSUBSCRIBE request - as defined in 'Section 4.1.4:
  1504           Cancelling a subscription with UNSUBSCRIBE' in [[!UPNP-DEVICEARCH11]] - with a HOST header set to that
  1505           <var>active service</var>'s <code>eventsUrl</code> property and a SID header set to the <var>callback
  1506           ID</var> obtained when the initial <a>setup a UPnP Events Subscription</a> action occurred.
  1507         </p>
  1508       </section>
  1509       <section>
  1510         <h5>
  1511           Discovery and Launch Protocol (<abbr title="Discovery and Launch Protocol">DIAL</abbr>)
  1512         </h5>
  1513         <p>
  1514           A user agent that implements DIAL service discovery MUST issue a <dfn>search request for DIAL-enabled
  1515           devices</dfn> against the user's current local network according to the full normative text and timing
  1516           provided in 'Section 1.3.2: Search request with M-SEARCH' detailed in [[!UPNP-DEVICEARCH11]].
  1517         </p>
  1518         <p>
  1519           Let <var>dial version</var> be the version number specified in the <a>valid service type</a> token. Let
  1520           <var>dial search target</var> be the concatentation of the
  1521           <code>urn:dial-multiscreen-org:service:dial:</code> string constant with the <var>dial version</var>
  1522           (currently, <var>dial version</var> can only be <code>1</code>)
  1523         </p>
  1524         <p>
  1525           The user agent MUST issue all <a title="search request for DIAL devices">search requests for DIAL devices</a>
  1526           with a HTTP request line equal to <code>M-SEARCH * HTTP/1.1</code>, with a HOST header equal to the reserved
  1527           multicast address and port of <code>239.255.255.250:1900</code>, a MAN header equal to
  1528           <code>ssdp:discover</code>, an ST header equal to <var>dial search target</var> and a user-agent defined MX
  1529           header equal to a <dfn>maximum DIAL advertisement response wait time</dfn> value between <code>1</code> and
  1530           <code>5</code> seconds.
  1531         </p>
  1532         <p>
  1533           The user agent MUST listen for any incoming responses to a <a>search request for DIAL devices</a>.
  1534         </p>
  1535         <p>
  1536           For each HTTP Response following an initial <a>search request for DIAL devices</a> sent on a <a>standard UPnP
  1537           address and port</a> the user agent MUST run the following steps:
  1538         </p>
  1539         <ol class="rule">
  1540           <li>If the HTTP Response is not a HTTP 200 OK response then this response is invalid and the user agent MUST
  1541           discard this response, abort any remaining steps and return. The user agent MAY issue a new <a>search request
  1542           for DIAL devices</a> as a result of this error occurring.
  1543           </li>
  1544           <li>If the <a>maximum DIAL advertisement response wait time</a> has been exceeded since the initial <a>search
  1545           request for DIAL devices</a> was sent then the <a>HTTP Response</a> is invalid and the user agent MUST
  1546           discard this response, abort any remaining steps and return. The user agent MAY stop listening for responses
  1547           from the current <a>search request for DIAL devices</a> as a result of this error occurring. Equally, the
  1548           user agent MAY issue a new <a>search request for DIAL devices</a> as a result of this error occurring.
  1549           </li>
  1550           <li>Let <var>dial device</var> be an Object with a property for each HTTP header received in the <a>HTTP
  1551           Response</a>, with each key being the name of a HTTP response header and each value being that HTTP response
  1552           header's value.
  1553           </li>
  1554           <li>If <var>dial device</var> does not contain at least one <var>CACHE-CONTROL</var> entry, at least one
  1555           <var>USN</var> entry, at least one <var>ST</var> entry and at least one <var>LOCATION</var> entry or the
  1556           value of its <var>ST</var> entry is not <var>dial search target</var>, then the <a>HTTP Response</a> is
  1557           invalid and the <a>user agent</a> MUST discard this response, abort any remaining steps and return.
  1558           </li>
  1559           <li>The user agent MUST run the rule for <a>obtaining a UPnP Device Description File</a> passing in the first
  1560           occurrence of <var>LOCATION</var> from <var>dial device</var> as the <var>device descriptor URL</var>
  1561           argument and the first occurrence of <var>USN</var> from <var>dial device</var> as the <var>device
  1562           identifier</var> argument and the first occurrence of <var>CACHE-CONTROL</var> from <var>dial device</var>
  1563           (minus the leading string of <code>max-age=</code>) as the <var>device expiry</var> argument.
  1564           </li>
  1565         </ol>
  1566         <p>
  1567           The rule for <dfn>obtaining a DIAL Device Description File</dfn> is the process of obtaining the contents of
  1568           a standard UPnP Device Description [[!UPNP-DEVICEARCH11]] from a URL-based resource. This rule takes three
  1569           arguments - <var>device descriptor URL</var>, <var>device identifier</var> and <var>device expiry</var> - and
  1570           when called the user agent MUST run the following steps:
  1571         </p>
  1572         <ol class="rule">
  1573           <li>Let <var>device descriptor file</var> contain the contents of the file located at the URL provided in
  1574           <var>device descriptor URL</var> obtained according to the rules defined in 'Section 2.11: Retrieving a
  1575           description using HTTP' in [[!UPNP-DEVICEARCH11]].
  1576           </li>
  1577           <li>Let <var>application url</var> be the value of the first occurrence of the <code>Application-URL</code>
  1578           response header field obtained according to the rules defined in 'Section 5.4: Device Description Response'
  1579           in [<a href="https://sites.google.com/a/dial-multiscreen.org/dial/dial-protocol-specification">DIAL</a>]
  1580           </li>
  1581           <li>If the value provided in <var>device descriptor URL</var> cannot be resolved as a reachable URL on the
  1582           current network or the <var>device descriptor file</var> remains empty or <var>application url</var> is
  1583           undefined then it is invalid and the <a>user agent</a> MUST abort any remaining steps and return.
  1584           </li>
  1585           <li>Run the following steps to add the newly discovered DIAL service:
  1586             <ol class="rule">
  1587               <li>Let <var>network service record</var> be a new Object consisting of the following empty properties:
  1588               <code>id</code>, <code>deviceId</code>, <code>name</code>, <code>type</code>, <code>url</code>,
  1589               <code>expiryTimestamp</code>.
  1590               </li>
  1591               <li>Set <var>network service record</var>'s <code>id</code> property to the first occurrence of the
  1592               <code>&lt;UDN&gt;</code> element in the <var>descriptor file</var> prefixed with the <code>dial:</code>
  1593               string constant
  1594               </li>
  1595               <li>Set <var>network service record</var>'s <code>deviceId</code> property to the value of <var>device
  1596               identifier</var>.
  1597               </li>
  1598               <li>Set <var>network service record</var>'s <code>name</code> property to the string value of the first
  1599               occurrence of the <code>&lt;friendlyName&gt;</code> element in the <var>descriptor file</var>.
  1600               </li>
  1601               <li>Set <var>network service record</var>'s <code>type</code> property to <var>dial search target</var>.
  1602               </li>
  1603               <li>Set <var>network service record</var>'s <code>url</code> property to the string value of the
  1604               <var>application url</var>.
  1605               </li>
  1606               <li>Set <var>network service record</var>'s <code>expiryTimestamp</code> property to the value of the
  1607               current date, in UTC timestamp format, plus the value of <var>device expiry</var>.
  1608               </li>
  1609               <li>Run the general rule for <a>adding an available service</a>, passing in the current <var>network
  1610               service record</var> as the only argument.
  1611               </li>
  1612             </ol>
  1613           </li>
  1614         </ol>
  1615       </section>
  1616       <section>
  1617         <h3>
  1618           Network Topology Monitoring
  1619         </h3>
  1620         <div>
  1621           <p>
  1622             When the <a>user agent</a> detects that the user has dropped from a connected network then, for each
  1623             <var>existing service record</var> in the <a>list of available service records</a> discovered via that
  1624             network connection, the <a>user agent</a> MUST run the general rule for <a>removing an available
  1625             service</a> passing in each <var>existing service record</var>'s <code>id</code> property as the only
  1626             argument for each call.
  1627           </p>
  1628           <p>
  1629             When the <a>user agent</a> detects that the user has connected to a new network or reconnected to an
  1630             existing network, then it SHOULD restart its discovery mechanisms as defined in the <a href=
  1631             "#service-discovery">Service Discovery</a> section of this specification, maintaining the existing <a>list
  1632             of active service managers</a> currently in use.
  1633           </p>
  1634         </div>
  1635       </section>
  1636     </section>
  1637     <section>
  1638       <h3>
  1639         Events Summary
  1640       </h3>
  1641       <p>
  1642         The following events are dispatched on the <a href="#networkservices"><code>NetworkServices</code></a> and/or
  1643         <a href="#networkservice"><code>NetworkService</code></a> objects:
  1644       </p>
  1645       <table border="1">
  1646         <thead>
  1647           <tr>
  1648             <th>
  1649               <span>Event name</span>
  1650             </th>
  1651             <th>
  1652               <span>Interface</span>
  1653             </th>
  1654             <th>
  1655               <span>Dispatched when...</span>
  1656             </th>
  1657           </tr>
  1658         </thead>
  1659         <tbody>
  1660           <tr>
  1661             <td>
  1662               <dfn id="event-serviceavailable"><code>serviceavailable</code></dfn>
  1663             </td>
  1664             <td>
  1665               <a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1666                   class="externalDFN"><code>Event</code></a>
  1667             </td>
  1668             <td>
  1669               When a <a>new service</a> that matches one of the <a>requested type tokens</a> is found in the current
  1670               network.
  1671             </td>
  1672           </tr>
  1673           <tr>
  1674             <td>
  1675               <dfn id="event-serviceunavailable"><code>serviceunavailable</code></dfn>
  1676             </td>
  1677             <td>
  1678               <a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1679                   class="externalDFN"><code>Event</code></a>
  1680             </td>
  1681             <td>
  1682               When an <a>existing service</a> that matches one of the <a>requested type tokens</a> gracefully leaves or
  1683               expires from the current network.
  1684             </td>
  1685           </tr>
  1686           <tr>
  1687             <td>
  1688               <dfn id="event-serviceonline"><code>serviceonline</code></dfn>
  1689             </td>
  1690             <td>
  1691               <a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1692                   class="externalDFN"><code>Event</code></a>
  1693             </td>
  1694             <td>
  1695               When a <a>current service</a> renews its service registration within the current network.
  1696             </td>
  1697           </tr>
  1698           <tr>
  1699             <td>
  1700               <dfn id="event-serviceoffline"><code>serviceoffline</code></dfn>
  1701             </td>
  1702             <td>
  1703               <a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1704                   class="externalDFN"><code>Event</code></a>
  1705             </td>
  1706             <td>
  1707               When a <a>current service</a> gracefully leaves or otherwise expires from the current network.
  1708             </td>
  1709           </tr>
  1710           <tr>
  1711             <td>
  1712               <dfn id="event-notify"><code>notify</code></dfn>
  1713             </td>
  1714             <td>
  1715               <a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1716                   class="externalDFN"><code>Event</code></a>
  1717             </td>
  1718             <td>
  1719               When a valid UPnP Events Subscription Message is received on a <a>user-agent generated callback url</a>
  1720               for a <a>current service</a>. This event never fires for Zeroconf-based services.
  1721             </td>
  1722           </tr>
  1723         </tbody>
  1724       </table>
  1725     </section>
  1726     <section>
  1727       <h3>
  1728         Garbage collection
  1729       </h3>
  1730       <p>
  1731         A user agent MUST only garbage collect a <a><code>NetworkServices</code></a> object and remove its entry from
  1732         the <a>list of active service managers</a> when the user has navigated away from the <a href=
  1733         "http://www.whatwg.org/specs/web-apps/current-work/complete/browsers.html#entry-script"
  1734            class="externalDFN">entry script</a>'s <a href=
  1735            "http://www.whatwg.org/specs/web-apps/current-work/complete/origin-0.html#origin"
  1736            class="externalDFN">origin</a> in which the current <a><code>NetworkServices</code></a> object was provided.
  1737       </p>
  1738       <p>
  1739         A user agent MUST NOT garbage collect individual <a><code>NetworkService</code></a> objects until their parent
  1740         <a><code>NetworkServices</code></a> object has been garbage collected.
  1741       </p>
  1742       <p>
  1743         A user agent MUST garbage collect the <a><code>NetworkService</code></a> <a>indexed properties</a> of a
  1744         <a><code>NetworkServices</code></a> object when that <a><code>NetworkServices</code></a> object itself has been
  1745         garbage-collected.
  1746       </p>
  1747     </section>
  1748     <section>
  1749       <h3>
  1750         Use Cases and Requirements
  1751       </h3>
  1752       <p>
  1753         This section covers what the requirements are for this API, as well as illustrates some use cases.
  1754       </p>
  1755       <ul class="rule">
  1756         <li>Once a user has given permission, user agents should provide the ability for Web pages to communicate
  1757         directly with a Local-networked Service.
  1758           <ul class="rule">
  1759             <li>Example: A web-based TV remote control. A Web page wants to control the current user's TV, changing the
  1760             programming shown or increasing/decreasing/muting the volume of the Local-networked Device. The Web page
  1761             requests a service type that is known to be implemented by television sets to which it has the application
  1762             logic to communicate. Local devices providing the request service types are discovered and presented to the
  1763             user for authorization. The user selects one or more of the discovered television sets to be accessible to
  1764             the current Web page and then clicks 'Share'. The Web page can now communicate directly with the
  1765             user-authorized Local-networked services.
  1766             </li>
  1767           </ul>
  1768         </li>
  1769         <li>Web pages should be able to communicate with Local-networked Services using the messaging channel supported
  1770         by those Devices.
  1771           <ul class="rule">
  1772             <li>Example: A Web page advertises that it is capable of controlling multiple Home Media Servers. The user
  1773             can select their Home Media Server type from a drop-down list, at which point the Web page sends a request
  1774             to the user agent to connect with the associated service type of the Home Media Server. The Media Server
  1775             selected implements a Web Socket channel for bi-directional service communication and so the Web page opens
  1776             a web socket to the requested Media Server and can communicate as required via that appropriate channel.
  1777             </li>
  1778           </ul>
  1779         </li>
  1780         <li>Web pages should be able to communicate with Local-networked Services using the messaging format supported
  1781         by those Devices.
  1782           <ul class="rule">
  1783             <li>Example: A Web page advertises that it is capable of interacting with and controlling multiple types of
  1784             Home Media Server. The user can select their Home Media Server type from a drop-down list or known Media
  1785             Servers, at which point the Web page sends a request to the user agent to connect with the associated
  1786             service type (and, optionally, the associated event type) of the Home Media Server. The communication
  1787             protocols supported by Home Media Servers typically vary between UPnP, JSON-RPC, Protocol Buffers or other
  1788             messaging formats depending on the Home Media Server requested. The Web page is able to communicate with
  1789             the user-selected Home Media Server in the messaging format supported by that Device, which, in this
  1790             example is a simple key/value pair text format.
  1791             </li>
  1792           </ul>
  1793         </li>
  1794         <li>Web pages should not be able to communicate with Local-networked Services that have not been authorized by
  1795         the user thereby maintaining the user's privacy.
  1796           <ul class="rule">
  1797             <li>Example: A Web page requests access to one type of Local-networked service. The user authorizes access
  1798             to that particular service. Other services running on that same device, and on other devices within the
  1799             network, should not be accessible to the current Web page.
  1800             </li>
  1801           </ul>
  1802         </li>
  1803         <li>A user should be able to share one or more Local-networked Services based on a particular service type
  1804         request from a Web page.
  1805           <ul class="rule">
  1806             <li>Example: A Web page is capable of interacting with a specific profile of Local-networked Service. As
  1807             such, it makes a request to the user agent to access those services, of which multiple matches are found.
  1808             The user is capable of selecting one or more of the discovered services to share with the Web page. The Web
  1809             page can then implement a drag-and-drop interface for the user to drag specific actions on to one or more
  1810             of the authorized Local-networked Services.
  1811             </li>
  1812           </ul>
  1813         </li>
  1814         <li>User agents should provide an API exposed to script that exposes the features above. The user is notified
  1815         by UI anytime interaction with Local-networked Services is requested, giving the user full ability to cancel or
  1816         abort the transaction. The user selects the Local-networked Services to be connected to the current Web page,
  1817         and can cancel these at any time. No invocations to these APIs occur silently without user intervention.
  1818         </li>
  1819       </ul>
  1820     </section>
  1821     <section class="informative appendix">
  1822       <h3>
  1823         Examples
  1824       </h3>
  1825       <div class="example">
  1826         <p>
  1827           This sample code exposes a button. When clicked, this button is disabled and the user is prompted to offer a
  1828           network service. The user may also select multiple network services. When the user has authorized a network
  1829           service to be connected to the web page then the web page issues a simple command to get a list of all the
  1830           albums stored on the connected media player service.
  1831         </p>
  1832         <p>
  1833           The button is re-enabled only when the connected network service disconnects for whatever reason (the service
  1834           becomes unavailable on the network, the user disconnects from their current network or the user revokes
  1835           access to the service from the current web page). At this point the user can re-click the button to select a
  1836           new network service to connect to the web page and the above steps are repeated.
  1837         </p>
  1838         <p>
  1839           The provided service type identifier and service interaction used in this example is based on the
  1840           well-defined service type and messaging format supported by the <a href="http://xbmc.org/about/">XBMC Media
  1841           Server</a>.
  1842         </p>
  1843         <hr>
  1844         <pre class="highlight">
  1845 &lt;input type="button" value="Start" onclick="start()" id="startBtn"/&gt;
  1846 &lt;div id="debugconsole"&gt;&lt;/div&gt;
  1847 
  1848 &lt;script&gt;
  1849  var startBtn = document.getElementById('startBtn'),
  1850      debug = document.getElementById('debugconsole');
  1851 
  1852  function start() {
  1853    if(navigator.getNetworkServices) {
  1854       navigator.getNetworkServices('zeroconf:_xbmc-jsonrpc._tcp', gotXBMCService, error);
  1855       startBtn.disabled = true;
  1856    } else {
  1857       debug.innerHTML += "&lt;br&gt;Service Discovery not supported!";
  1858    }
  1859  }
  1860 
  1861  function gotXBMCService(services) {
  1862 
  1863 // Listen for service disconnect messages
  1864 
  1865    services[0].addEventListener('serviceoffline', function ( e ) {
  1866        debug.innerHTML += "&lt;br&gt;" + services[0].name + " disconnected.";
  1867        startBtn.disabled = false;
  1868    }, false);
  1869 
  1870 // Send a service message to get albums list (and process the service response)
  1871 
  1872    var svcXhr = new XMLHttpRequest();
  1873    svcXhr.open("POST", services[0].url + "/getAlbums"); // services[0].url and its sub-resources have been
  1874                                                         // whitelisted for cross-site XHR use in this
  1875                                                         // current browsing context.
  1876 
  1877    svcXhr.setRequestHeader('Content-Type', 'application/json-rpc');
  1878 
  1879    svcXhr.addEventListener('readystatechange', function ( response ) {
  1880      if( response.readyState != 4 || response.status != 200 )
  1881         return;
  1882      debug.innerHTML += "&lt;br&gt;" + services[0].name + " response received: ";
  1883      debug.textContent += JSON.parse(response.responseText);
  1884    }, false);
  1885 
  1886    var svcMsg = [
  1887      { "jsonrpc": "2.0", "method": "AudioLibrary.GetAlbums", "params": { "genreid": -1,
  1888          "artistid": -1, "start": -1, "end": -1 }, "id": "1" }
  1889    ];
  1890 
  1891    svcXhr.send(JSON.stringify(svcMsg));
  1892    debug.innerHTML += "&lt;br&gt;" + services[0].name + " request sent: ";
  1893    debug.textContent += JSON.stringify(svcMsg);
  1894 
  1895  }
  1896 
  1897  function error( err ) {
  1898    debug.innerHTML += "&lt;br&gt;An error occurred obtaining a local network service.";
  1899    startBtn.disabled = false;
  1900  }
  1901 &lt;/script&gt;
  1902 </pre>
  1903       </div>
  1904       <div class="example">
  1905         <p>
  1906           This sample exposes a drop-down list containing a number of common Home-based audio devices. When the user
  1907           selects an audio device from the list provided, they are prompted to authorize a network service based on the
  1908           service type requested. The user may also select multiple network services matching the selected service
  1909           type. In this example, the user selects their make as being <var>Sony</var> and their model as being
  1910           <var>Bravia S1000</var> from which the Web page can derive a service type
  1911           (<var>urn:schemas-upnp-org:service:RenderingControl:1</var>).<br>
  1912           <br>
  1913           Once the user has authorized the device, the web page sends a simple mute command according to the messaging
  1914           format supported by the device.
  1915         </p>
  1916         <hr>
  1917         <pre class="highlight">
  1918 &lt;select name="make" id="make"&gt;
  1919   &lt;option selected="selected" disabled="disabled"&gt;Select make&lt;/option&gt;
  1920   &lt;option&gt;Sony&lt;/option&gt;
  1921   &lt;option&gt;Philips&lt;/option&gt;
  1922   &lt;option&gt;Alba&lt;/option&gt;
  1923 &lt;/select&gt;
  1924 &lt;select name="model" id="model"&gt;&lt;/select&gt;
  1925 &lt;div id="debugconsole"&gt;&lt;/div&gt;
  1926 
  1927 &lt;script&gt;
  1928   var debug = document.getElementById('debugconsole');
  1929 
  1930   var models = {
  1931     "Sony": [
  1932       {"name": "Bravia TV S1000", "type": "upnp", "service": "urn:schemas-upnp-org:service:RenderingControl:1" },
  1933       {"name": "Bravia TV S2000", "type": "zeroconf", "service": "_mediarenderer._http._tcp" },
  1934       {"name": "HiFi WD10", "type": "upnp", "service": "urn:schemas-upnp-org:service:RenderingControl:1" }
  1935     ],
  1936     "Philips": [ /* ... */ ],
  1937     "Alba": [ /* ... */ ]
  1938   };
  1939 
  1940   var makeEl = document.getElementById("make"),
  1941       modelEl = document.getElementById("model");
  1942 
  1943   makeEl.addEventListener('change', function() {
  1944     modelEl.innerHTML = ""; // reset
  1945     var defaultOption = document.createElement("option");
  1946     defaultOption.textContent = "Select model";
  1947     defaultOption.setAttribute("disabled", "disabled");
  1948     defaultOption.setAttribute("selected", "selected");
  1949     modelEl.appendChild(defaultOption);
  1950     for(var i = 0, l = models[makeEl.value].length; i &lt; l; i++) {
  1951       var option = document.createElement("option");
  1952       option.textContent = models[makeEl.value][i]["name"];
  1953       option.setAttribute("value", models[makeEl.value][i]["type"] + ":" + models[makeEl.value][i]["service"]);
  1954       modelEl.appendChild(option);
  1955     }
  1956   }, false);
  1957 
  1958   modelEl.addEventListener('change', function() {
  1959     if(navigator.getNetworkServices &amp;&amp;
  1960          modelEl.value == "upnp:urn:schemas-upnp-org:service:RenderingControl:1") {
  1961       navigator.getNetworkServices(modelEl.value, successCallback, errorCallback);
  1962     } else if (modelEl.value == "zeroconf:_mediarenderer._http._tcp") {
  1963       debug.innerHTML += "&lt;br&gt;Service type is not implemented by this application.";
  1964     } else {
  1965       debug.innerHTML += "&lt;br&gt;Service Discovery is not supported!";
  1966     }
  1967   }, false);
  1968 &lt;/script&gt;
  1969 
  1970 &lt;script&gt;
  1971   function successCallback( services ) {
  1972 
  1973   // Listen for service push notification messages
  1974 
  1975     services[0].addEventListener('notify', function ( msg ) {
  1976          debug.innerHTML += "&lt;br&gt;" + services[0].name + " event received: ";
  1977          debug.textContent += msg.data;
  1978     }, false);
  1979 
  1980  // Send a control signal to mute the service audio
  1981 
  1982     var svcXhr = new XMLHttpRequest();
  1983     svcXhr.open("POST", services[0].url); // services[0].url and its
  1984                                           // sub-resources have been whitelisted for
  1985                                           // cross-site XHR use in this current
  1986                                           // browsing context.
  1987 
  1988     svcXhr.setRequestHeader('SOAPAction', 'urn:schemas-upnp-org:service:RenderingControl:1#SetMute');
  1989     svcXhr.setRequestHeader('Content-Type', 'text/xml; charset="utf-8";');
  1990 
  1991     svcXhr.onreadystatechange = function ( response ) {
  1992       if( response.readyState != 4 || response.status != 200 )
  1993         return;
  1994       debug.innerHTML += "&lt;br&gt;" + services[0].name + " response received: ";
  1995       debug.textContent += response.responseXML;
  1996     }
  1997 
  1998     // Service messaging to mute the provided service
  1999     var svcMsg = '&lt;?xml version="1.0" encoding="utf-8"?&gt;' +
  2000                  '&lt;s:Envelope s:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" ' +
  2001                    'xmlns:s="http://schemas.xmlsoap.org/soap/envelope/"&gt;' +
  2002                    '&lt;s:Body&gt;' +
  2003                      '&lt;u:SetMute xmlns:u="urn:schemas-upnp-org:service:RenderingControl:1"&gt;' +
  2004                        '&lt;InstanceID&gt;0&lt;/InstanceID&gt;' +
  2005                        '&lt;Channel&gt;Master&lt;/Channel&gt;' +
  2006                        '&lt;DesiredMute&gt;true&lt;/DesiredMute&gt;' +
  2007                      '&lt;/u:SetMute&gt;' +
  2008                    '&lt;/s:Body&gt;' +
  2009                  '&lt;/s:Envelope&gt;';
  2010 
  2011     svcXhr.send(svcMsg);
  2012     debug.innerHTML += "&lt;br&gt;" + services[0].name + " request sent: ";
  2013     debug.textContent += svcMsg;
  2014   }
  2015 
  2016   function errorCallback( error ) {
  2017     debug.innerHTML += "&lt;br&gt;An error occurred: " + error.code;
  2018   }
  2019 &lt;/script&gt;
  2020 </pre>
  2021       </div>
  2022     </section>
  2023     <section>
  2024       <h3>
  2025         Acknowledgements
  2026       </h3>
  2027       <p>
  2028         Thanks are expressed by the editor to the following individuals for their feedback on this specification to
  2029         date (in alphabetical order):<br>
  2030         <br>
  2031         Gar Bergstedt, Lars-Erik Bolstad, Cathy Chan, Hari G Kumar, Bob Lund, Giuseppe Pascale, Marcin Simonides,
  2032         Clarke Stevens, Christian Söderström, Mark Vickers.
  2033       </p>
  2034       <p>
  2035         Thanks are also expressed by the editor to the following organizations and groups for their support in
  2036         producing this specification to date (in alphabetical order):<br>
  2037         <br>
  2038         CableLabs, Opera Software ASA, W3C Device APIs Working Group, W3C Web and TV Interest Group.
  2039       </p>
  2040     </section>
  2041   </body>
  2042 </html>