discovery-api/Overview.src.html
author Rich Tibbett <richt@opera.com>
Tue, 05 Feb 2013 15:21:33 +0100
changeset 378 89d1cef16d35
parent 377 a311e7fe116c
child 387 abb49f62a775
permissions -rw-r--r--
Only remove UPnP Events subscription once it is no longer in use by any active services
     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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    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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    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             },
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    51               name:       "Clarke Stevens",
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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     </section>
   295     <section>
   296       <h2>
   297         Requesting networked services
   298       </h2>
   299       <pre class="widl">
   300 [Supplemental, NoInterfaceObject]
   301 interface <dfn id="navigatornetworkservice">NavigatorNetworkService</dfn> {
   302   // Obtain a Local-networked Service
   303   void <a href="#dom-navigator-getnetworkservices">getNetworkServices</a>( in any type,
   304                            in <a href=
   305 "#navigatornetworkservicesuccesscallback">NavigatorNetworkServiceSuccessCallback</a> successCallback,
   306                            in optional <a href=
   307 "#navigatornetworkserviceerrorcallback">NavigatorNetworkServiceErrorCallback</a> errorCallback );
   308 };
   309 <a class="externalDFN"
   310      href=
   311      "http://www.whatwg.org/specs/web-apps/current-work/complete/timers.html#navigator">Navigator</a> implements <a href=
   312      "#navigatornetworkservice">NavigatorNetworkService</a>;
   313 
   314 [Callback=FunctionOnly, NoInterfaceObject]
   315 interface <dfn id="navigatornetworkservicesuccesscallback">NavigatorNetworkServiceSuccessCallback</dfn> {
   316   void handleEvent( in <a href="#networkservices">NetworkServices</a> services );
   317 };
   318 
   319 [NoInterfaceObject]
   320 interface <dfn id="navigatornetworkserviceerror">NavigatorNetworkServiceError</dfn> {
   321   const unsigned short <a href="#dom-navigatornetworkserviceerror-permission_denied">PERMISSION_DENIED_ERR</a> = 1;
   322   const unsigned short <a href="#dom-navigatornetworkserviceerror-unknown_type_prefix">UNKNOWN_TYPE_PREFIX_ERR</a> = 2;
   323   readonly attribute unsigned short <a href="#dom-navigatornetworkserviceerror-code">code</a>;
   324 };
   325 
   326 [Callback=FunctionOnly, NoInterfaceObject]
   327 interface <dfn id="navigatornetworkserviceerrorcallback">NavigatorNetworkServiceErrorCallback</dfn> {
   328   void handleEvent( in <a href="#navigatornetworkserviceerror">NavigatorNetworkServiceError</a> error );
   329 };
   330 </pre>
   331       <section>
   332         <h2>
   333           Methods
   334         </h2>
   335         <dl class="domintro">
   336           <dt>
   337             <var title="">window</var> . <code title="dom-navigator"><a href=
   338             "http://www.whatwg.org/specs/web-apps/current-work/complete/timers.html#navigator">navigator</a></code> .
   339             <code title="dom-navigator-getNetworkServices"><a href=
   340             "#dom-navigator-getnetworkservices">getNetworkServices</a></code> ( <var title="">type</var> , <var title=
   341             "">successCallback</var> [, <var title="">errorCallback</var> ] )
   342           </dt>
   343           <dd>
   344             <p>
   345               Prompts the user to select discovered network services that have advertised support for the requested
   346               service type.
   347             </p>
   348             <p>
   349               The <var title="">type</var> argument contains one or more <a>valid service type</a> tokens that the web
   350               page would like to interact with.
   351             </p>
   352             <p>
   353               If the user accepts, the <var title="">successCallback</var> is invoked, with zero or more <a href=
   354               "#networkservice"><code>NetworkService</code></a> objects as its argument.
   355             </p>
   356             <p>
   357               If the user declines, the <var title="">errorCallback</var> (if any) is invoked.
   358             </p>
   359           </dd>
   360         </dl>
   361         <div>
   362           <p>
   363             When the <dfn id="dom-navigator-getnetworkservices"
   364                title="dom-navigator-getnetworkservices"><code>getNetworkServices(type, successCallback[,
   365                errorCallback])</code></dfn> method is called, the <a>user agent</a> MUST run the following steps:
   366           </p>
   367           <ol class="rule">
   368             <li>Let <var>requested control types</var> be initially set to an empty array.
   369             </li>
   370             <li>If <var>type</var> is an array consisting of one or more <a>valid service type</a> tokens, then let
   371             <var>requested control types</var> by the value of <var>type</var>, removing any non-<a>valid service
   372             type</a> tokens from the resulting array.
   373             </li>
   374             <li>If <var>type</var> is a string consisting of one <a>valid service type</a> token, then let
   375             <var>requested control types</var> be an array containing one item with a value of <var>type</var>.
   376             </li>
   377             <li>If <var>requested control types</var> is an array that contains at least one or more <a title=
   378             "valid service type">valid service type</a> tokens then continue to the step labeled <em>process</em>
   379             below. Otherwise, the <a>user agent</a> MUST <a href=
   380             "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
   381                   class="externalDFN">queue a task</a> to invoke <var>errorCallback</var>, if it is provided and is an
   382                   object of type <code>Function</code>, with a new <a href=
   383                   "#navigatornetworkserviceerror"><code>NavigatorNetworkServiceError</code></a> object whose <a href=
   384                   "#dom-navigatornetworkserviceerror-code"><code>code</code></a> attribute has the numeric value 2
   385                   (<a href=
   386                   "#dom-navigatornetworkserviceerror-unknown_type_prefix"><code>UNKNOWN_TYPE_PREFIX_ERR</code></a>) as
   387                   its argument, abort any remaining steps and return.
   388             </li>
   389             <li>
   390               <em>Process</em>: Let <var>services found</var> be an empty array.
   391             </li>
   392             <li>For each <var>available service</var> in the <a>list of available service records</a> run the following
   393             steps:
   394               <ol class="rule">
   395                 <li>For each <var>requested control type</var> in <var>requested control types</var>: If <var>available
   396                 service</var>'s <code>type</code> attribute equals the <var>requested control type</var> then let <var>
   397                   matched service</var> equal the value of <var>available service</var> and continue at the step
   398                   labeled <var>attach</var> below.
   399                 </li>
   400                 <li>Continue at the next <var>available service</var>.
   401                 </li>
   402                 <li>
   403                   <em>Attach</em>: If <var>matched service</var> is not empty then run the following steps:
   404                   <ol class="rule">
   405                     <li>Let <var>new service object</var> be a new <a href=
   406                     "#networkservice"><code>NetworkService</code></a> object, mapping the parameters of <var>matched
   407                     service</var> to this new object where possible.
   408                     </li>
   409                     <li>Append <var>new service object</var> to the <var>services found</var> array.
   410                     </li>
   411                   </ol>
   412                 </li>
   413               </ol>
   414             </li>
   415             <li>Return, and run the remaining steps asynchronously.
   416             </li>
   417             <li>Optionally, e.g. based on a previously-established user preference, for security reasons, or due to
   418             platform limitations, the <a>user agent</a> MAY <a href=
   419             "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
   420                   class="externalDFN">queue a task</a> to invoke <var>errorCallback</var>, if it is provided and is an
   421                   object of type <code>Function</code>, with a new <a href=
   422                   "#navigatornetworkserviceerror"><code>NavigatorNetworkServiceError</code></a> object whose <a href=
   423                   "#dom-navigatornetworkserviceerror-code"><code>code</code></a> attribute has the numeric value 1
   424                   (<a href=
   425                   "#dom-navigatornetworkserviceerror-permission_denied"><code>PERMISSION_DENIED_ERR</code></a>) as its
   426                   argument, abort any remaining steps and return.
   427             </li>
   428             <li>The user agent MUST NOT provide the entry script's origin with a <a href=
   429             "#networkservices"><code>NetworkServices</code></a> object without prior permission given by the user.
   430               <p>
   431                 If <var>services found</var> is not an empty array then the <a>user agent</a> MAY choose to prompt the
   432                 user in a user-agent-specific manner for permission to provide the <a href=
   433                 "http://www.whatwg.org/specs/web-apps/current-work/complete/browsers.html#entry-script"
   434                    class="externalDFN">entry script</a>'s <a href=
   435                    "http://www.whatwg.org/specs/web-apps/current-work/complete/origin-0.html#origin"
   436                    class="externalDFN">origin</a> with a <a href="#networkservices"><code>NetworkServices</code></a>
   437                    object representing the <a>user-authorized</a> subset of <var>services found</var>.
   438               </p>
   439               <p>
   440                 Alternatively, the user agent MAY choose to queue a task to invoke <var>successCallback</var> or
   441                 <var>errorCallback</var> immediately based on a previously-established user preference, for security
   442                 reasons, or due to platform limitations. In such an implementation, if <var>successCallback</var> is to
   443                 be fired as a result of a previously-established user preference then the <a>user agent</a> MUST
   444                 continue at the next step of this algorithm.
   445               </p>
   446               <p>
   447                 If permission has been granted by the user to access one or more networked services then the <a>user
   448                 agent</a> SHOULD include an "ongoing local-network communication" indicator.
   449               </p>
   450               <p>
   451                 If permission has been denied by the user, <a>user agent</a> or platform, then the <a>user agent</a>
   452                 MUST <a href="http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
   453                    class="externalDFN">queue a task</a> to invoke <var>errorCallback</var>, if it is provided and is an
   454                    object of type <code>Function</code>, with a new <a href=
   455                    "#navigatornetworkserviceerror"><code>NavigatorNetworkServiceError</code></a> object whose <a href=
   456                    "#dom-navigatornetworkserviceerror-code"><code>code</code></a> attribute has the numeric value 1
   457                    (<a href=
   458                    "#dom-navigatornetworkserviceerror-permission_denied"><code>PERMISSION_DENIED_ERR</code></a>) as its
   459                    argument, abort any remaining steps and return.
   460               </p>
   461               <p>
   462                 If the user never responds or no previously-established user preference has been met, this algorithm
   463                 stalls on this step.
   464               </p>
   465             </li>
   466             <li>Let <var>services</var> be an empty array.
   467             </li>
   468             <li>If <var>services found</var> is not an empty array then set <var>services</var> to be an array of one
   469             or more <a href="#networkservice"><code>NetworkService</code></a> objects for which the user granted
   470             permission above - known as the current objects <dfn>user-authorized</dfn> services.
   471             </li>
   472             <li>Remove all previously whitelisted urls from the <a>entry script origin's URL whitelist</a> granted in
   473             the current <a href="http://www.whatwg.org/specs/web-apps/current-work/complete/browsers.html#entry-script"
   474                   class="externalDFN">entry script</a>'s <a href=
   475                   "http://www.whatwg.org/specs/web-apps/current-work/complete/origin-0.html#origin"
   476                   class="externalDFN">origin</a>.
   477             </li>
   478             <li>For each Object <var>service</var> in <var>services</var>, if any, run the following sub-steps:
   479               <ol class="rule">
   480                 <li>Add the <var>service</var>'s <code>url</code> parameter to the <a>entry script origin's
   481                   <abbr title="Uniform Resource Locator">URL</abbr> whitelist</a>.
   482                 </li>
   483                 <li>If <var>service</var>'s <code>type</code> parameter begins with the DOMString "<code>upnp:</code>"
   484                 and the <var>service</var>'s <code>eventsUrl</code> parameter is not empty then <a>setup a UPnP Events
   485                 Subscription</a> for <var>service</var>.
   486                 </li>
   487               </ol>
   488             </li>
   489             <li>Let <var>services manager</var> be a new <a href="#networkservices"><code>NetworkServices</code></a>
   490             object.
   491             </li>
   492             <li>Store <var>requested control types</var> against <var>services manager</var> as an internal variable.
   493             </li>
   494             <li>Set <var>services manager</var>'s <a href=
   495             "#dom-networkservices-servicesavailable"><code>servicesAvailable</code></a> attribute to the number of
   496             items currently found in the <a>list of available service records</a> whose <code>type</code> property
   497             matches any of the tokens requested in <var>requested control types</var>.
   498             </li>
   499             <li>Add <var>services</var>, if any, to the <var>services manager</var> object as its collection of
   500             <a>indexed properties</a>. If <var>services</var> is an empty array then the <var>services manager</var>
   501             does not have any <var>indexed properties</var>.
   502             </li>
   503             <li>Set <var>services manager</var>'s <a href="#dom-networkservices-length"><code>length</code></a>
   504             attribute to the number of items in <var>services</var>.
   505             </li>
   506             <li>Add <var>services manager</var> to the <a>list of active service managers</a>.
   507             </li>
   508             <li>The <a>user agent</a> MUST <a href=
   509             "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
   510                   class="externalDFN">queue a task</a> to invoke <var>successCallback</var> with <var>services
   511                   manager</var> as its argument.
   512             </li>
   513           </ol>
   514           <p>
   515             The <a href="http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#task-source"
   516                class="externalDFN">task source</a> for these <a href=
   517                "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#concept-task"
   518                class="externalDFN">tasks</a> is the <a href=
   519                "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#user-interaction-task-source"
   520                class="externalDFN">user interaction task source</a>.
   521           </p>
   522           <p>
   523             When a <a href="#networkservice"><code>NetworkService</code></a> object is provided to a Web page, the
   524             <a>user agent</a> MUST add the <code>url</code> property to the <dfn>entry script origin's URL
   525             whitelist</dfn>. This list enables the Web page to override and initiate cross-site resource requests
   526             towards these URLs, and any sub-resources of these URLs, within the current <a href=
   527             "http://www.whatwg.org/specs/web-apps/current-work/complete/browsers.html#entry-script"
   528                class="externalDFN">entry script</a>'s <a href=
   529                "http://www.whatwg.org/specs/web-apps/current-work/complete/origin-0.html#origin"
   530                class="externalDFN">origin</a> via various existing mechanisms (e.g. Web Sockets, Server-Sent Events,
   531                Web Messaging, XMLHttpRequest).
   532           </p>
   533           <p>
   534             If the user navigates away from the <a href=
   535             "http://www.whatwg.org/specs/web-apps/current-work/complete/browsers.html#entry-script"
   536                class="externalDFN">entry script</a>'s <a href=
   537                "http://www.whatwg.org/specs/web-apps/current-work/complete/origin-0.html#origin"
   538                class="externalDFN">origin</a> then the <a>user agent</a> <em class="ct">MUST</em> remove all previously
   539                whitelisted urls from the <a>entry script origin's URL whitelist</a>. There is no persistence to network
   540                service selections provided to a web page. It is not possible to access a previously white-listed
   541                networked service without the necessary user authorization in all of the following cases:
   542           </p>
   543           <ul>
   544             <li>If the current script is reloaded at any point in the same or different window.
   545             </li>
   546             <li>if the current script reinvokes the <a href=
   547             "#dom-navigator-getnetworkservices"><code>getNetworkServices()</code></a> method at any point in its
   548             execution.
   549             </li>
   550             <li>If the user navigates forward or back in their history to reload the current page.
   551             </li>
   552             <li>If a script is running in a different origin.
   553             </li>
   554           </ul>
   555         </div>
   556       </section>
   557       <section>
   558         <h3>
   559           Error Handling
   560         </h3>
   561         <dl class="domintro">
   562           <dt>
   563             <var title="">error</var> . <code title="dom-NavigatorNetworkServiceError-code"><a href=
   564             "#dom-navigatornetworkserviceerror-code">code</a></code>
   565           </dt>
   566           <dd>
   567             <p>
   568               Returns the current error's error code. At the current time, this will be <code>1</code> or
   569               <code>2</code>, for which the corresponding error constants <a href=
   570               "#dom-navigatornetworkserviceerror-permission_denied"><code>PERMISSION_DENIED_ERR</code></a> and <a href=
   571               "#dom-navigatornetworkserviceerror-unknown_type_prefix"><code>UNKNOWN_TYPE_PREFIX_ERR</code></a> are
   572               defined.
   573             </p>
   574           </dd>
   575         </dl>
   576         <p>
   577           The <dfn id="dom-navigatornetworkserviceerror-code"
   578              title="dom-navigatornetworkserviceerror-code"><code>code</code></dfn> attribute of a <a href=
   579              "#navigatornetworkserviceerror"><code>NavigatorNetworkServiceError</code></a> object <em class=
   580              "ct">MUST</em> return the code for the error, which will be one of the following:
   581         </p>
   582         <dl>
   583           <dt>
   584             <dfn id="dom-navigatornetworkserviceerror-permission_denied"
   585                 title="dom-navigatornetworkserviceerror-permission_denied"><code>PERMISSION_DENIED_ERR</code></dfn>
   586                 (numeric value 1)
   587           </dt>
   588           <dd>
   589             The user or user agent denied the page permission to access any services.
   590           </dd>
   591           <dt>
   592             <dfn id="dom-navigatornetworkserviceerror-unknown_type_prefix"
   593                 title="dom-navigatornetworkserviceerror-unknown_type_prefix"><code>UNKNOWN_TYPE_PREFIX_ERR</code></dfn>
   594                 (numeric value 2)
   595           </dt>
   596           <dd>
   597             No <a>valid service type</a> tokens were provided in the method invocation.
   598           </dd>
   599         </dl>
   600       </section>
   601     </section>
   602     <section>
   603       <h2>
   604         Obtaining networked services
   605       </h2>
   606       <p>
   607         The <a href="#networkservices"><code>NetworkServices</code></a> interface represents a collection of zero or
   608         more <dfn>indexed properties</dfn> that are each a <a>user-authorized</a> <a href=
   609         "#networkservice"><code>NetworkService</code></a> object.
   610       </p>
   611       <p>
   612         A <a href="#networkservices"><code>NetworkServices</code></a> object is the top level success callback
   613         parameter from a call to <a href="#dom-navigator-getnetworkservices"><code>getNetworkServices()</code></a>.
   614       </p>
   615       <pre class="widl">
   616 [NoInterfaceObject]
   617 interface <dfn id="networkservices">NetworkServices</dfn> {
   618   readonly attribute unsigned long    <a href="#dom-networkservices-length">length</a>;
   619   getter <a href="#networkservice">NetworkService</a> (unsigned long index);
   620   <a href="#networkservice">NetworkService</a>? <a href=
   621 "#dom-networkservices-getservicebyid">getServiceById</a>(DOMString id);
   622 
   623   readonly attribute unsigned long    <a href="#dom-networkservices-servicesavailable">servicesAvailable</a>;
   624 
   625   // event handler attributes
   626            attribute <a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#eventhandler"
   627      class="externalDFN">EventHandler</a>     <a href="#dom-networkservices-onserviceavailable">onserviceavailable</a>;
   628            attribute <a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#eventhandler"
   629      class="externalDFN">EventHandler</a>     <a href=
   630      "#dom-networkservices-onserviceunavailable">onserviceunavailable</a>;
   631 
   632 };
   633 
   634 <a href="#networkservices">NetworkServices</a> implements <a href=
   635 "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#interface-eventtarget"
   636      class="externalDFN">EventTarget</a>;
   637 </pre>
   638       <section>
   639         <h2>
   640           Attributes
   641         </h2>
   642         <dl class="domintro">
   643           <dt>
   644             <code title="dom-networkservices-length"><a href="#dom-networkservices-length">length</a></code>
   645           </dt>
   646           <dd>
   647             <p>
   648               Returns the current number of items in the current object's collection of <a href=
   649               "#networkservice"><code>NetworkService</code></a> objects.
   650             </p>
   651           </dd>
   652           <dt>
   653             <code title="dom-networkservices-servicesavailable"><a href=
   654             "#dom-networkservices-servicesavailable">servicesAvailable</a></code>
   655           </dt>
   656           <dd>
   657             <p>
   658               Returns the current number of items matching one of the app-requested <a>valid service type</a> tokens in
   659               the <a>list of available service records</a>.
   660             </p>
   661           </dd>
   662         </dl>
   663         <div>
   664           <p>
   665             The <dfn id="dom-networkservices-length"><code>length</code></dfn> attribute MUST return the number of
   666             <a href="#networkservice"><code>NetworkService</code></a> objects represented by the collection.
   667           </p>
   668           <p>
   669             The <dfn id="dom-networkservices-servicesavailable"><code>servicesAvailable</code></dfn> attribute MUST
   670             return the number of services in the <a>list of available service records</a> whose <code>type</code>
   671             attribute matches any of the <a>valid service type</a> tokens that was initially used to create the current
   672             <a href="#networkservices"><code>NetworkServices</code></a> object.
   673           </p>
   674         </div>
   675       </section>
   676       <section>
   677         <h2>
   678           Methods
   679         </h2>
   680         <dl class="domintro">
   681           <dt>
   682             <code title="networkservices-getter"><a href="#networkservices">services</a></code> [ <var title=
   683             "">index</var> ]
   684           </dt>
   685           <dd>
   686             <p>
   687               Returns the specified <a href="#networkservice"><code>NetworkService</code></a> object.
   688             </p>
   689           </dd>
   690           <dt>
   691             <code title="networkservices-getter"><a href="#networkservices">services</a></code> . <code title=
   692             "dom-networkservices-getservicebyid"><a href=
   693             "#dom-networkservices-getservicebyid">getServiceById</a></code> ( <var title="">id</var> )
   694           </dt>
   695           <dd>
   696             <p>
   697               Returns the <a href="#networkservice"><code>NetworkService</code></a> object with the given identifier,
   698               or null if no service has that identifier.
   699             </p>
   700           </dd>
   701         </dl>
   702         <p>
   703           A <a href="#networkservices"><code>NetworkServices</code></a> object represents the current collection of
   704           zero or more <a href="#networkservice"><code>NetworkService</code></a> objects - its <a>indexed
   705           properties</a>. A <a href="#networkservices"><code>NetworkServices</code></a> object is
   706           <span>immutable</span> meaning that <a>indexed properties</a> cannot be added and <a>indexed properties</a>
   707           cannot be removed for the lifetime of a <a href="#networkservices"><code>NetworkServices</code></a> object.
   708         </p>
   709         <p class="note">
   710           Each service in a <a href="#networkservices"><code>NetworkServices</code></a> object thus has an index; the
   711           first has the index 0, and each subsequent service is numbered one higher than the previous one.
   712         </p>
   713         <p>
   714           The <a href=
   715           "http://www.whatwg.org/specs/web-apps/current-work/multipage/infrastructure.html#supported-property-indices"
   716              class="externalDFN">supported property indices</a> of <a href=
   717              "#networkservices"><code>NetworkServices</code></a> objects at any instant are the numbers from zero to
   718              the number of the <a href="#networkservice"><code>NetworkService</code></a> objects in the collection
   719              minus one.
   720         </p>
   721         <p>
   722           To <a href=
   723           "http://www.whatwg.org/specs/web-apps/current-work/multipage/infrastructure.html#determine-the-value-of-an-indexed-property"
   724              class="externalDFN">determine the value of an indexed property</a> for a given index <var>index</var> in a
   725              <a href="#networkservices"><code>NetworkServices</code></a> object the user agent MUST return the <a href=
   726              "#networkservice"><code>NetworkService</code></a> object that represents the <var>index</var>th item in
   727              the collection.
   728         </p>
   729         <p>
   730           The <dfn id="dom-networkservices-getservicebyid"><code>getServiceById(id)</code></dfn> method <em class=
   731           "ct">MUST</em> return the first <a href="#networkservice"><code>NetworkService</code></a> object in the
   732           collection whose <a href="#dom-networkservice-id"><code>id</code></a> attribute is equal to the value of the
   733           <var>id</var> argument provided. When no <a href="#networkservice"><code>NetworkService</code></a> objects
   734           match the given argument, the method MUST return null.
   735         </p>
   736         <p>
   737           Services available within the local network can connect and disconnect at different times during the
   738           execution of a web page. A <a>user agent</a> can inform a web page when the state of networked services
   739           matching the requested <a>valid service type</a> change. Web pages can use this information to enable in-page
   740           experiences for communicating the state of networked services with the ability to change the particular
   741           service or set of services the page is connected to by re-invoking the <a href=
   742           "#dom-navigator-getnetworkservices"><code>getNetworkServices()</code></a> method.
   743         </p>
   744       </section>
   745       <section>
   746         <h2>
   747           Events
   748         </h2>
   749         <p>
   750           The following are the event handlers (and their corresponding event handler event types) that <em class=
   751           "ct">MUST</em> be supported, as IDL attributes, by all objects implementing the <a href=
   752           "#networkservices"><code>NetworkServices</code></a> interface:
   753         </p>
   754         <table border="1">
   755           <thead>
   756             <tr>
   757               <th>
   758                 <span title="event handlers">Event handler</span>
   759               </th>
   760               <th>
   761                 <span>Event handler event type</span>
   762               </th>
   763             </tr>
   764           </thead>
   765           <tbody>
   766             <tr>
   767               <td>
   768                 <dfn id="dom-networkservices-onserviceavailable"
   769                     title="dom-NetworkServices-onserviceavailable"><code>onserviceavailable</code></dfn>
   770               </td>
   771               <td>
   772                 <a href="#event-serviceavailable"><code>serviceavailable</code></a>
   773               </td>
   774             </tr>
   775             <tr>
   776               <td>
   777                 <dfn id="dom-networkservices-onserviceunavailable"
   778                     title="dom-NetworkServices-onserviceunavailable"><code>onserviceunavailable</code></dfn>
   779               </td>
   780               <td>
   781                 <a href="#event-serviceunavailable"><code>serviceunavailable</code></a>
   782               </td>
   783             </tr>
   784           </tbody>
   785         </table>
   786       </section>
   787     </section>
   788     <section>
   789       <h2>
   790         Communicating with a networked service
   791       </h2>
   792       <p>
   793         The <a href="#networkservice"><code>NetworkService</code></a> interface is used to provide a set of connection
   794         information for an HTTP service endpoint and if available, service events, running on a networked device.
   795       </p>
   796       <pre class="widl">
   797 [NoInterfaceObject]
   798 interface <dfn id="networkservice">NetworkService</dfn> {
   799   readonly attribute DOMString        <a href="#dom-networkservice-id">id</a>;
   800   readonly attribute DOMString        <a href="#dom-networkservice-name">name</a>;
   801   readonly attribute DOMString        <a href="#dom-networkservice-type">type</a>;
   802   readonly attribute DOMString        <a href="#dom-networkservice-url">url</a>;
   803   readonly attribute DOMString        <a href="#dom-networkservice-config">config</a>;
   804 
   805   readonly attribute boolean          <a href="#dom-networkservice-online">online</a>;
   806 
   807   // event handler attributes
   808            attribute <a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#eventhandler"
   809      class="externalDFN">EventHandler</a>     <a href="#dom-networkservice-onserviceonline">onserviceonline</a>;
   810            attribute <a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#eventhandler"
   811      class="externalDFN">EventHandler</a>     <a href="#dom-networkservice-onserviceoffline">onserviceoffline</a>;
   812 
   813            attribute <a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#eventhandler"
   814      class="externalDFN">EventHandler</a>     <a href="#dom-networkservice-onnotify">onnotify</a>;
   815 };
   816 
   817 <a href="#networkservice">NetworkService</a> implements <a href=
   818 "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#interface-eventtarget"
   819      class="externalDFN">EventTarget</a>;
   820 </pre>
   821       <section>
   822         <h2>
   823           Attributes
   824         </h2>
   825         <dl class="domintro">
   826           <dt>
   827             <var title="">service</var> . <code title="dom-networkservice-id"><a href=
   828             "#dom-networkservice-id">id</a></code>
   829           </dt>
   830           <dd>
   831             <p>
   832               A unique identifier for the given user-selected service instance.
   833             </p>
   834           </dd>
   835           <dt>
   836             <var title="">service</var> . <code title="dom-networkservice-name"><a href=
   837             "#dom-networkservice-name">name</a></code>
   838           </dt>
   839           <dd>
   840             <p>
   841               The name of the user-selected service.
   842             </p>
   843           </dd>
   844           <dt>
   845             <var title="">service</var> . <code title="dom-networkservice-type"><a href=
   846             "#dom-networkservice-type">type</a></code>
   847           </dt>
   848           <dd>
   849             <p>
   850               The <a>valid service type</a> token value of the user-selected service.
   851             </p>
   852           </dd>
   853           <dt>
   854             <var title="">service</var> . <code title="dom-networkservice-url"><a href=
   855             "#dom-networkservice-url">url</a></code>
   856           </dt>
   857           <dd>
   858             <p>
   859               The control URL endpoint (including any required port information) of the user-selected control service
   860               that has been added to the <a>entry script origin's URL whitelist</a>.
   861             </p>
   862           </dd>
   863           <dt>
   864             <var title="">service</var> . <code title="dom-networkservice-config"><a href=
   865             "#dom-networkservice-config">config</a></code>
   866           </dt>
   867           <dd>
   868             <p>
   869               The configuration information associated with the service depending on the requested service type.
   870             </p>
   871           </dd>
   872         </dl>
   873         <p>
   874           The <dfn id="dom-networkservice-id"><code>id</code></dfn> attribute is a unique identifier for the service.
   875           The same service provided at different times or on different objects MUST have the same <a href=
   876           "#dom-networkservice-id"><code>id</code></a> value.
   877         </p>
   878         <p>
   879           The <dfn id="dom-networkservice-name"><code>name</code></dfn> attribute represents a human-readable title for
   880           the service.
   881         </p>
   882         <p>
   883           The <dfn id="dom-networkservice-type"><code>type</code></dfn> attribute reflects the value of the <a>valid
   884           service type</a> of the service.
   885         </p>
   886         <p>
   887           The <dfn id="dom-networkservice-url"><code>url</code></dfn> attribute is an <a href=
   888           "http://www.w3.org/TR/html5/urls.html#absolute-url"
   889              class="externalDFN">absolute URL</a> pointing to the root HTTP endpoint for the service that has been
   890              added to the <a>entry script origin's URL whitelist</a>. Web pages can subsequently use this value for
   891              implicit cross-document messaging via various existing mechanisms (e.g. Web Sockets, Server-Sent Events,
   892              Web Messaging, XMLHttpRequest).
   893         </p>
   894         <p>
   895           The <dfn id="dom-networkservice-config"><code>config</code></dfn> attribute provides the raw configuration
   896           information extracted from the given network service.
   897         </p>
   898       </section>
   899       <section>
   900         <h3>
   901           States
   902         </h3>
   903         <dl class="domintro">
   904           <dt>
   905             <var title="">service</var> . <code title="dom-networkservice-online"><a href=
   906             "#dom-networkservice-online">online</a></code>
   907           </dt>
   908           <dd>
   909             <p>
   910               Returns <code>true</code> if the service is reporting that it is accessible on the local network or
   911               <code>false</code> if the service is reporting that it is no longer accessible (temporarily or
   912               permanently) on the local network.
   913             </p>
   914           </dd>
   915         </dl>
   916         <p>
   917           The <dfn id="dom-networkservice-online"><code>online</code></dfn> attribute indicates whether the service is
   918           reporting itself as being either <var>online</var>, and therefore accessible on the local network, in which
   919           case this attribute will return <code>true</code> or, <var>offline</var>, and therefore not accessible on the
   920           local network, either temporarily or permanently, in which case this attribute will return
   921           <code>false</code>. This attribute MUST default to <code>true</code>.
   922         </p>
   923       </section>
   924       <section>
   925         <h3>
   926           Events
   927         </h3>
   928         <p>
   929           The following are the event handlers (and their corresponding event handler event types) that <em class=
   930           "ct">MUST</em> be supported, as IDL attributes, by all objects implementing the <a href=
   931           "#networkservice"><code>NetworkService</code></a> interface:
   932         </p>
   933         <table border="1">
   934           <thead>
   935             <tr>
   936               <th>
   937                 <span title="event handlers">Event handler</span>
   938               </th>
   939               <th>
   940                 <span>Event handler event type</span>
   941               </th>
   942             </tr>
   943           </thead>
   944           <tbody>
   945             <tr>
   946               <td>
   947                 <dfn id="dom-networkservice-onnotify"
   948                     title="dom-NetworkService-onnotify"><code>onnotify</code></dfn>
   949               </td>
   950               <td>
   951                 <a href="#event-notify"><code>notify</code></a>
   952               </td>
   953             </tr>
   954             <tr>
   955               <td>
   956                 <dfn id="dom-networkservice-onserviceonline"
   957                     title="dom-NetworkService-onserviceonline"><code>onserviceonline</code></dfn>
   958               </td>
   959               <td>
   960                 <a href="#event-serviceonline"><code>serviceonline</code></a>
   961               </td>
   962             </tr>
   963             <tr>
   964               <td>
   965                 <dfn id="dom-networkservice-onserviceoffline"
   966                     title="dom-NetworkService-onserviceoffline"><code>onserviceoffline</code></dfn>
   967               </td>
   968               <td>
   969                 <a href="#event-serviceoffline"><code>serviceoffline</code></a>
   970               </td>
   971             </tr>
   972           </tbody>
   973         </table>
   974       </section>
   975     </section>
   976     <section>
   977       <h2>
   978         Service Discovery
   979       </h2>
   980       <p>
   981         A <a>user agent</a> conforming to this specification MAY implement <abbr title=
   982         "Simple Service Discovery Protocol">SSDP</abbr> [[!UPNP-DEVICEARCH11]], Zeroconf [[!DNS-SD]] + [[!MDNS]] and/or
   983         <abbr title="Discovery and Launch Protocol">DIAL</abbr> [<a href=
   984         "https://sites.google.com/a/dial-multiscreen.org/dial/dial-protocol-specification">DIAL</a>] <dfn>service
   985         discovery mechanisms</dfn> - the requirements detailed in this section of the specification - to enable Web
   986         pages to request and connect with HTTP services running on networked devices, discovered via any of these
   987         mechanisms, through this API. When a <a>user agent</a> implements any of these <a>service discovery
   988         mechanisms</a>, then it MUST conform to the corresponding algorithms provided in this section of the
   989         specification.
   990       </p>
   991       <p>
   992         This section presents how the results of these <a>service discovery mechanisms</a> will be matched to requested
   993         service types, how the user agent stores available and active services and how their properties are applied to
   994         any resulting <a href="#networkservice"><code>NetworkService</code></a> objects.
   995       </p>
   996       <p>
   997         It is expected that user agents will perform these <a>service discovery mechanisms</a> asynchronously and
   998         periodically update the <a>list of available service records</a> as required. The timing of any <a>service
   999         discovery mechanisms</a> is an implementation detail left to the discretion of the implementer (e.g. by
  1000         continuously monitoring the network as a background process or on invocation of this API from a Web page).
  1001       </p>
  1002       <p>
  1003         The <dfn>list of available service records</dfn> is a single dynamic internal lookup table within user agents
  1004         that is used to track all the services that have been discovered and are available in the current network at
  1005         the current time. At any point during the running of either of the two <a>service discovery mechanisms</a> then
  1006         existing entries within this table can be updated, entries can be added and entries can be removed as the
  1007         status of networked services changes according to the rules defined in this specification.
  1008       </p>
  1009       <p>
  1010         The <dfn>list of active service managers</dfn> is an internal list within user agents that is used to track all
  1011         <a href="#networkservices"><code>NetworkServices</code></a> objects currently being shared with any web pages
  1012         at the current time within the user agent. Each <a href="#networkservices"><code>NetworkServices</code></a>
  1013         object in the <a>list of active service managers</a> represents a collection of zero or more <a href=
  1014         "#networkservice"><code>NetworkService</code></a> objects - known as its <dfn>indexed properties</dfn>.
  1015         <a href="#networkservice"><code>NetworkService</code></a> objects are attached as the <a>indexed properties</a>
  1016         of a <a href="#networkservices"><code>NetworkServices</code></a> object as part of the <a href=
  1017         "#dom-navigator-getnetworkservices"><code>getNetworkServices()</code></a> algorithm.
  1018       </p>
  1019       <p>
  1020         The rule for <dfn>adding an available service</dfn> is the process of adding a new service or updating an
  1021         existing service that is generally available on the user's current network in the <a>list of available service
  1022         records</a>. This rule takes one argument, <var>network service record</var>, and consists of running the
  1023         following steps:
  1024       </p>
  1025       <ol class="rule">
  1026         <li>For each <var>existing service record</var> in the current <a>list of available service records</a>, run
  1027         the following sub-steps:
  1028           <ol class="rule">
  1029             <li>If the <var>existing service record</var>'s <code>id</code> property does not equal <var>network
  1030             service record</var>'s <code>id</code> property then abort any remaining sub-steps and continue at the next
  1031             available <var>existing service record</var>.
  1032             </li>
  1033             <li>Replace the value of <var>existing service record</var> in the current <a>list of available service
  1034             records</a> with the value of <var>network service record</var>, aborting any remaining steps in this
  1035             algorithm and return.
  1036             </li>
  1037           </ol>
  1038         </li>
  1039         <li>Add <var>network service record</var> to the <a>list of available service records</a> as a new item.
  1040         </li>
  1041         <li>For each <var>service manager</var> in the <a>list of active service managers</a> run the following steps:
  1042           <ol class="rule">
  1043             <li>For each <var>active service</var> in <var>service manager</var> run the following steps:
  1044               <ol class="rule">
  1045                 <li>If the <var>network service record</var>'s <code>id</code> property equals the <var>active
  1046                 service</var>'s <code>id</code> attribute then set <var>active service</var>'s <a href=
  1047                 "#dom-networkservice-online"><code>online</code></a> attribute to <code>true</code> and then <a href=
  1048                 "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
  1049                       class="externalDFN">queue a task</a> to dispatch a newly created event with the name <a href=
  1050                       "#event-serviceonline"><code>serviceonline</code></a> that uses the <a href=
  1051                       "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1052                       class="externalDFN"><code>Event</code></a> interface, which does not bubble, is not cancellable,
  1053                       and has no default action, at the current <var>active service</var> object.
  1054                 </li>
  1055               </ol>
  1056             </li>
  1057             <li>Let <var>'service type in current service manager' flag</var> be <code>false</code>.
  1058             </li>
  1059             <li>For each <var>requested control type</var> of the <var>requested control types</var> in <var>service
  1060             manager</var> run the following steps:
  1061               <ol class="rule">
  1062                 <li>If <var>network service record</var>'s <code>type</code> property does not equal <var>requested
  1063                 control type</var> then abort any remaining sub-steps and continue at the next available <var>requested
  1064                 control type</var>.
  1065                 </li>
  1066                 <li>Set the <var>'service type in current service manager' flag</var> to <code>true</code>, abort any
  1067                 remaining sub-steps and continue.
  1068                 </li>
  1069               </ol>
  1070             </li>
  1071             <li>If the <var>'service type in current service manager' flag</var> is set to <code>true</code> then
  1072             increment <var>service manager</var>'s <a href=
  1073             "#dom-networkservices-servicesavailable"><code>servicesAvailable</code></a> attribute by <code>1</code> and
  1074             then <a href="http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
  1075                   class="externalDFN">queue a task</a> to dispatch a newly created event with the name <a href=
  1076                   "#event-serviceavailable"><code>serviceavailable</code></a> that uses the <a href=
  1077                   "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1078                   class="externalDFN"><code>Event</code></a> interface, which does not bubble, is not cancellable, and
  1079                   has no default action, at the current <var>service manager</var> object.
  1080             </li>
  1081           </ol>
  1082         </li>
  1083       </ol>
  1084       <p>
  1085         The rule for <dfn>removing an available service</dfn> is the general process of removing a service from the
  1086         <a>list of available service records</a> that has left the user's current network or has otherwise expired.
  1087         This rule takes one argument, <var>service identifier</var>, and consists of running the following steps:
  1088       </p>
  1089       <ol class="rule">
  1090         <li>For each <var>existing service record</var> in the current <a>list of available service records</a>, run
  1091         the following sub-steps:
  1092           <ol class="rule">
  1093             <li>If the <var>existing service record</var>'s <code>id</code> property does not match <var>service
  1094             identifier</var> then skip any remaining sub-steps for the current <var>existing service record</var> and
  1095             continue at the next available <var>existing service record</var>.
  1096             </li>
  1097             <li>Let <var>'service type in use' flag</var> be <code>false</code>.
  1098             </li>
  1099             <li>For each <var>service manager</var> in the <a>list of active service managers</a> run the following
  1100             steps:
  1101               <ol class="rule">
  1102                 <li>Let <var>'service type in current service manager' flag</var> be <code>false</code>.
  1103                 </li>
  1104                 <li>For each <var>active service</var> in <var>service manager</var> run the following steps:
  1105                   <ol class="rule">
  1106                     <li>If <var>existing service record</var>'s <code>id</code> property equals the <var>active
  1107                     service</var>'s <code>id</code> attribute and <var>active service</var>'s <a href=
  1108                     "#dom-networkservice-online"><code>online</code></a> attribute is currently set to
  1109                     <code>true</code> then set <var>active service</var>'s <a href="#dom-networkservice-online"><code>
  1110                       online</code></a> attribute to <code>false</code> and then <a href=
  1111                       "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
  1112                           class="externalDFN">queue a task</a> to dispatch a newly created event with the name <a href=
  1113                           "#event-serviceoffline"><code>serviceoffline</code></a> that uses the <a href=
  1114                           "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1115                           class="externalDFN"><code>Event</code></a> interface, which does not bubble, is not
  1116                           cancellable, and has no default action, at the current <var>active service</var>.
  1117                     </li>
  1118                   </ol>
  1119                 </li>
  1120                 <li>For each <var>requested control type</var> of the <var>requested control types</var> in
  1121                 <var>service manager</var> run the following steps:
  1122                   <ol class="rule">
  1123                     <li>If <var>existing service record</var>'s <code>type</code> property does not equal
  1124                     <var>requested control type</var> then abort any remaining sub-steps and continue at the next
  1125                     available <var>requested control type</var>.
  1126                     </li>
  1127                     <li>Set the <var>'service type in current service manager' flag</var> to <code>true</code> and the
  1128                     <var>'service type in use' flag</var> to <code>true</code>, abort any remaining sub-steps and
  1129                     continue.
  1130                     </li>
  1131                   </ol>
  1132                 </li>
  1133                 <li>If the <var>'service type in current service manager' flag</var> is set to <code>true</code> then
  1134                 decrement <var>service manager</var>'s <a href=
  1135                 "#dom-networkservices-servicesavailable"><code>servicesAvailable</code></a> attribute by <code>1</code>
  1136                 and then <a href=
  1137                 "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
  1138                       class="externalDFN">queue a task</a> to dispatch a newly created event with the name <a href=
  1139                       "#event-serviceunavailable"><code>serviceunavailable</code></a> that uses the <a href=
  1140                       "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1141                       class="externalDFN"><code>Event</code></a> interface, which does not bubble, is not cancellable,
  1142                       and has no default action, at the current <var>service manager</var> object.
  1143                 </li>
  1144               </ol>
  1145             </li>
  1146             <li>If the <var>'service type in use' flag</var> is <code>false</code> and the <var>existing service
  1147             record</var>'s <code>type</code> property begins with the DOMString "<code>upnp:</code>" and <var>existing
  1148             service record</var>'s <code>eventsURL</code> property is set then run the rule to <a>terminate an existing
  1149             UPnP Events Subscription</a>, if one is currently active (as a result of having previously called <a>setup
  1150             a UPnP Events Subscription</a> against the current <var>existing service record</var>).
  1151             </li>
  1152             <li>Remove <var>existing service record</var> from the current <a>list of available service records</a>.
  1153             </li>
  1154           </ol>
  1155         </li>
  1156       </ol>
  1157       <p>
  1158         User agents SHOULD expire a service record from the <a>list of available service records</a> when its
  1159         <code>expiryTimestamp</code> attribute exceeds the current UTC timestamp. When this condition is met the
  1160         <a>user agent</a> SHOULD run the rule for <a>removing an available service</a>, passing in the expired service
  1161         record's <code>id</code> attribute as the only argument.
  1162       </p>
  1163       <section>
  1164         <h4>
  1165           Zeroconf (<abbr title="Multicast DNS">mDNS</abbr> + <abbr title="Domain Name System">DNS</abbr>-<abbr title=
  1166           "Service Discovery">SD</abbr>)
  1167         </h4>
  1168         <p>
  1169           For each DNS response received from a user-agent-initiated Multicast DNS Browse for <abbr title=
  1170           "DNS Pointer Record">PTR</abbr> records with the name <code>_services._dns-sd._udp</code> on the resolved
  1171           recommended automatic browsing domain [[!MDNS]], the <a>user agent</a> MUST run the following steps:
  1172         </p>
  1173         <ol class="rule">
  1174           <li>Let <var>service mDNS responses</var> be an array of PTR records received by issuing a Multicast DNS
  1175           Browse for PTR records with the name of the current discovered service type.
  1176           </li>
  1177           <li>For each Object <var>service mDNS response</var> in <var>service mDNS responses</var>, run the following
  1178           steps:
  1179             <ol>
  1180               <li>Let <var>network service record</var> be an Object consisting of the following empty properties:
  1181               <code>id</code>, <code>name</code>, <code>type</code>, <code>url</code>, <code>config</code>,
  1182               <code>expiryTimestamp</code>.
  1183               </li>
  1184               <li>Set <var>network service record</var>'s <code>id</code> property to the value of the full PTR Service
  1185               Instance Name [[!MDNS]].
  1186               </li>
  1187               <li>Set <var>network service record</var>'s <code>name</code> property to the value of the PTR Service
  1188               Instance Name's <var>Instance</var> component [[!MDNS]].
  1189               </li>
  1190               <li>Set <var>network service record</var>'s <code>type</code> property to the concatenation of the string
  1191               <code>zeroconf:</code> followed be the value of the PTR Service Instance Name's <var>Service</var>
  1192               component [[!MDNS]].
  1193               </li>
  1194               <li>Set <var>network service record</var>'s <code>url</code> property to the resolvable Service URL
  1195               obtained from performing an DNS-SD Lookup [[!DNS-SD]] of the current service from the PTR record provided
  1196               [[!MDNS]].
  1197               </li>
  1198               <li>Set <var>network service record</var>'s <code>config</code> property to the string value of the
  1199               contents of the first DNS-SD TXT record associated with the <var>service mDNS response</var> as defined
  1200               in [[!DNS-SD]].
  1201               </li>
  1202               <li>Set <var>network service record</var>'s <code>expiryTimestamp</code> property to the value of the
  1203               current date, in UTC timestamp format, plus a value of <code>120</code> seconds.
  1204               </li>
  1205               <li>Run the general rule for <a>adding an available service</a>, passing in the current <var>network
  1206               service record</var> as the only argument.
  1207               </li>
  1208             </ol>
  1209           </li>
  1210         </ol>
  1211       </section>
  1212       <section>
  1213         <h5>
  1214           Simple Service Discovery Protocol (<abbr title="Simple Service Discovery Protocol">SSDP</abbr>)
  1215         </h5>
  1216         <p>
  1217           A user agent that implements UPnP service discovery MUST issue a <dfn>search request for UPnP root
  1218           devices</dfn> against the user's current local network according to the full normative text and timing
  1219           provided in 'Section 1.3.2: Search request with M-SEARCH' detailed in [[!UPNP-DEVICEARCH11]].
  1220         </p>
  1221         <p>
  1222           The user agent MUST issue all <a title="search request for UPnP root devices">search requests for UPnP root
  1223           devices</a> with a HTTP request line equal to <code>M-SEARCH * HTTP/1.1</code>, with a HOST header equal to
  1224           the reserved multicast address and port of <code>239.255.255.250:1900</code> and a MAN header equal to
  1225           <code>ssdp:discover</code>. The <a>user agent</a> must also send an ST header with this HTTP request equal to
  1226           the String value of <code>ssdp:all</code> or <code>upnp:rootdevice</code> or a single <a>valid service
  1227           type</a> token. The user-agent MUST also send an MX header equal to a <dfn>maximum UPnP advertisement
  1228           response wait time</dfn> value between <code>1</code> and <code>5</code> seconds with this HTTP request.
  1229         </p>
  1230         <p>
  1231           The user agent MUST listen for any incoming responses to any <a>search request for UPnP root devices</a>.
  1232         </p>
  1233         <p>
  1234           For each <dfn>HTTP Response</dfn> following an initial <a>search request for UPnP root devices</a> sent on a
  1235           <a>standard UPnP address and port</a> the user agent MUST run the following steps:
  1236         </p>
  1237         <ol class="rule">
  1238           <li>If the <a>HTTP Response</a> is not a HTTP 200 OK response then this response is invalid and the user
  1239           agent MUST discard this response, abort any remaining steps and return. The user agent MAY issue a new
  1240           <a>search request for UPnP root devices</a> as a result of this error occurring.
  1241           </li>
  1242           <li>If the <a>maximum UPnP advertisement response wait time</a> has been exceeded since the initial <a>search
  1243           request for UPnP root devices</a> was sent then the <a>HTTP Response</a> is invalid and the user agent MUST
  1244           discard this response, abort any remaining steps and return. The user agent MAY stop listening for responses
  1245           from the current <a>search request for UPnP root devices</a> as a result of this error occurring. Equally,
  1246           the user agent MAY issue a new <a>search request for UPnP root devices</a> as a result of this error
  1247           occurring.
  1248           </li>
  1249           <li>Let <var>ssdp device</var> be an Object with a property for each HTTP header received in the <a>HTTP
  1250           Response</a>, with each key being the name of a HTTP response header and each value being that HTTP response
  1251           header's value.
  1252           </li>
  1253           <li>If <var>ssdp device</var> does not contain at least one <var>CACHE-CONTROL</var> entry, at least one
  1254           <var>USN</var> entry, at least one <var>ST</var> entry and at least one <var>LOCATION</var> entry then the
  1255           <a>HTTP Response</a> is invalid and the <a>user agent</a> MUST discard this response, abort any remaining
  1256           steps and return.
  1257           </li>
  1258           <li>The user agent MUST run the rule for <a>obtaining a UPnP Device Description File</a> passing in the first
  1259           occurrence of <var>LOCATION</var> from <var>ssdp device</var> as the <var>device descriptor URL</var>
  1260           argument and the first occurrence of <var>USN</var> from <var>ssdp device</var> as the <var>device
  1261           identifier</var> argument and the first occurrence of <var>CACHE-CONTROL</var> from <var>ssdp device</var>
  1262           (minus the leading string of <code>max-age=</code>) as the <var>device expiry</var> argument.
  1263           </li>
  1264         </ol>
  1265         <p>
  1266           The user agent MUST listen for incoming requests on the <dfn>standard UPnP address and port</dfn> on all
  1267           current local network interface addresses with the port <code>1900</code>.
  1268         </p>
  1269         <p>
  1270           For each <dfn>HTTP Request</dfn> received on a <a>standard UPnP address and port</a> the user agent MUST run
  1271           the following steps:
  1272         </p>
  1273         <ol class="rule">
  1274           <li>If the <a>HTTP Request</a> is not a HTTP NOTIFY request then it is not a valid UPnP Request and the user
  1275           agent MUST discard this request, abort any remaining steps and return.
  1276           </li>
  1277           <li>Let <var>ssdp device</var> be an Object with a property for each HTTP header received in the <a>HTTP
  1278           Request</a>, with each key being the name of a HTTP header and each value being that HTTP header's value.
  1279           </li>
  1280           <li>If <var>ssdp device</var>'s <var>NTS</var> entry is equal to <code>ssdp:alive</code> and the <a>HTTP
  1281           Request</a> does not contain at least one <var>CACHE-CONTROL</var> entry, at least one <var>USN</var> entry,
  1282           at least one <var>NT</var> entry, at least one <var>NTS</var> entry and at least one <var>LOCATION</var>
  1283           entry, then the <a>user agent</a> MUST discard this request, abort any remaining steps and return.
  1284           </li>
  1285           <li>If <var>ssdp device</var>'s <var>NTS</var> entry is equal to <code>ssdp:alive</code> then the user agent
  1286           MUST run the rule for <a>obtaining a UPnP Device Description File</a> passing in the first occurrence of
  1287           <var>LOCATION</var> from <var>ssdp device</var> as the <var>device descriptor URL</var> argument and the
  1288           first occurrence of <var>USN</var> from <var>ssdp device</var> as the <var>device identifier</var> argument
  1289           and the first occurrence of <var>CACHE-CONTROL</var> from <var>ssdp device</var> (minus the leading string of
  1290           <code>max-age=</code>) as the <var>device expiry</var>.<br>
  1291             <br>
  1292             Otherwise, if <var>ssdp device</var>'s <var>NTS</var> entry is equal to <code>ssdp:byebye</code> then the
  1293             user agent MUST run the rule for <a>removing all services from a registered UPnP Device</a> passing in the
  1294             first occurrence of <var>USN</var> from <var>ssdp device</var> as the <var>device identifier</var>
  1295             argument.
  1296           </li>
  1297         </ol>
  1298         <p>
  1299           The rule for <dfn>obtaining a UPnP Device Description File</dfn> is the process of obtaining the contents of
  1300           a standard UPnP Device Description [[!UPNP-DEVICEARCH11]] from a URL-based resource. This rule takes three
  1301           arguments - <var>device descriptor URL</var>, <var>device identifier</var> and <var>device expiry</var> - and
  1302           when called the user agent MUST run the following steps:
  1303         </p>
  1304         <ol class="rule">
  1305           <li>Let <var>device descriptor file</var> contain the contents of the file located at the URL provided in
  1306           <var>device descriptor URL</var> obtained according to the rules defined in 'Section 2.11: Retrieving a
  1307           description using HTTP' in [[!UPNP-DEVICEARCH11]].
  1308           </li>
  1309           <li>If the value provided in <var>device descriptor URL</var> cannot be resolved as a reachable URL on the
  1310           current network or the <var>device descriptor file</var> remains empty then it is invalid and the <a>user
  1311           agent</a> MUST abort any remaining steps and return.
  1312           </li>
  1313           <li>Run the rule for <a>processing a UPnP Device Description File</a>, passing in the current <var>device
  1314           descriptor file</var>, <var>device identifier</var> and <var>device expiry</var> arguments.
  1315           </li>
  1316         </ol>
  1317         <p>
  1318           The rule for <dfn>processing a UPnP Device Description File</dfn> is the process of parsing the contents of a
  1319           standard UPnP Device Description [[!UPNP-DEVICEARCH11]] and registering the UPnP services contained therein
  1320           within the <a>list of available service records</a>.
  1321         </p>
  1322         <p>
  1323           The rule for <a>processing a UPnP Device Description File</a> takes three arguments - <var>device descriptor
  1324           file</var>, <var>device identifier</var> and <var>device expiry</var> - and when called the user agent MUST
  1325           run the following steps:
  1326         </p>
  1327         <ol class="rule">
  1328           <li>Let <var>advertised services</var> be a list of all advertised services obtained from the <var>device
  1329           descriptor file</var> containing the value of the first occurrence of the <code>&lt;serviceList&gt;</code>
  1330           element as it is defined in 'Section 2.3: Device Description' in [[!UPNP-DEVICEARCH11]].
  1331           </li>
  1332           <li>For each <code>&lt;service&gt;</code> element - known as an <var>advertised service</var> - in
  1333           <var>advertised services</var> run the following steps:
  1334             <ol class="rule">
  1335               <li>Let <var>network service record</var> be a new Object consisting of the following empty properties:
  1336               <code>id</code>, <code>deviceId</code>, <code>name</code>, <code>type</code>, <code>url</code>,
  1337               <code>eventsUrl</code>, <code>config</code>, <code>expiryTimestamp</code>.
  1338               </li>
  1339               <li>Set <var>network service record</var>'s <code>id</code> property to the concatenated string value of
  1340               the first occurrence of the <code>&lt;UDN&gt;</code> element in the <var>device descriptor file</var>
  1341               with the <var>advertised service</var>'s <code>&lt;serviceId&gt;</code> sub-element.
  1342               </li>
  1343               <li>Set <var>network service record</var>'s <code>deviceId</code> property to the value of <var>device
  1344               identifier</var>.
  1345               </li>
  1346               <li>Set <var>network service record</var>'s <code>name</code> property to the string value of the first
  1347               occurrence of the <var>advertised service</var>'s <code>&lt;serviceId&gt;</code> sub-element.
  1348               </li>
  1349               <li>Set <var>network service record</var>'s <code>type</code> property to the concatenation of the string
  1350               <code>upnp:</code> followed by the string value of the first occurrence of the <var>advertised
  1351               service</var>'s <code>&lt;serviceType&gt;</code> sub-element.
  1352               </li>
  1353               <li>Set <var>network service record</var>'s <code>url</code> property to the string value of the first
  1354               occurrence of the <var>advertised service</var>'s <code>&lt;controlURL&gt;</code> sub-element.
  1355               </li>
  1356               <li>Set <var>network service record</var>'s <code>config</code> property to the string value of the
  1357               contents of the first occurrence of the <code>&lt;device&gt;</code> element in the <var>device descriptor
  1358               file</var>.
  1359               </li>
  1360               <li>If <var>advertised service</var>'s <code>&lt;eventSubURL&gt;</code> sub-element is not empty, then
  1361               set <var>network service record</var>'s <code>eventsUrl</code> property to the string value of the first
  1362               occurrence of the <var>advertised service</var>'s <code>&lt;eventSubURL&gt;</code> sub-element.
  1363               Otherwise, do not set <var>network service record</var>'s <code>eventsUrl</code> property.
  1364               </li>
  1365               <li>Set <var>network service record</var>'s <code>expiryTimestamp</code> property to the value of the
  1366               current date, in UTC timestamp format, plus the value of <var>device expiry</var>.
  1367               </li>
  1368               <li>Run the general rule for <a>adding an available service</a>, passing in the current <var>network
  1369               service record</var> as the only argument.
  1370               </li>
  1371             </ol>
  1372           </li>
  1373           <li>If <var>device descriptor file</var> contains a <code>&lt;deviceList&gt;</code> element then for each
  1374           <code>&lt;device&gt;</code> element within <code>&lt;deviceList&gt;</code> - herein known as an <var>embedded
  1375           device descriptor file</var> - the user agent MUST run the rule for <a>processing a UPnP Device Description
  1376           File</a>, passing in the current <var>embedded device descriptor file</var> as the <var>device descriptor
  1377           file</var> argument, along with the current <var>device identifier</var> and <var>device expiry</var>
  1378           arguments.
  1379           </li>
  1380         </ol>
  1381         <p>
  1382           The rule for <dfn>removing all services from a registered UPnP Device</dfn> is the process of removing all
  1383           services associated with a device from the <a>list of available service records</a> that has left the user's
  1384           current network or has otherwise timed out or expired. This rule takes one argument, <var>device
  1385           identifier</var>, and consists of running the following steps:
  1386         </p>
  1387         <ol class="rule">
  1388           <li>For each <var>existing service record</var> in the current <a>list of available service records</a>, run
  1389           the following sub-steps:
  1390             <ol class="rule">
  1391               <li>If the <var>existing service record</var>'s <code>deviceId</code> property does not match <var>device
  1392               identifier</var> then skip any remaining sub-steps for the current <var>existing service record</var> and
  1393               continue at the next available <var>existing service record</var>.
  1394               </li>
  1395               <li>Run the general rule for <a>removing an available service</a> passing in <var>existing service
  1396               record</var>'s <code>id</code> property as the only argument.
  1397               </li>
  1398             </ol>
  1399           </li>
  1400         </ol>
  1401         <p>
  1402           When the <a>user agent</a> is to <dfn>setup a UPnP Events Subscription</dfn>, it is to run the following
  1403           steps with the current <var>network service record</var> object as defined in 'Section 4.1.2: SUBSCRIBE with
  1404           NT and CALLBACK' in [[!UPNP-DEVICEARCH11]]:
  1405         </p>
  1406         <ol class="rule">
  1407           <li>If <var>network service record</var>'s <code>eventsUrl</code> property is empty then the <a>user
  1408           agent</a> MUST abort these steps.
  1409           </li>
  1410           <li>Let <var>callback URL</var> be the value of creating a new <a>user-agent generated callback url</a>.
  1411           </li>
  1412           <li>Send a HTTP SUBSCRIBE request with a <em>NT</em> header with a string value of <code>upnp:event</code>, a
  1413           <em>TIMEOUT</em> header with a user-agent defined timeout value (in the form <code>Second-XX</code> where
  1414           <code>XX</code> is the user-agent defined timeout value in seconds) and a <em>CALLBACK</em> header with a
  1415           string value of <var>callback URL</var> towards the <var>network service record</var>'s
  1416           <code>eventsUrl</code> property.
  1417           </li>
  1418           <li>If a non-200 OK response is received from the HTTP SUBSCRIBE request then the <a>user agent</a> MUST
  1419           abort these steps.
  1420           </li>
  1421           <li>On receiving a valid 200 OK response, run the following steps:
  1422             <ol class="rule">
  1423               <li>Let <var>callback ID</var> equal the string value of the first included <em>SID</em> header, if it
  1424               exists.
  1425               </li>
  1426               <li>Let <var>timeout date</var> equal the sum of the current UTC date value plus the integer value of the
  1427               first included <em>TIMEOUT</em> header (minus the leading string of <code>Second-</code>), if it exists.
  1428               </li>
  1429               <li>Run the following steps asynchronously and continue to the step labeled <em>listen</em> below.
  1430               </li>
  1431               <li>
  1432                 <em>Refresh Subscription</em>: Run the following steps at a set interval (X) within the <a>user
  1433                 agent</a>:
  1434                 <ol class="rule">
  1435                   <li>Let <var>current date</var> equal the current UTC date.
  1436                   </li>
  1437                   <li>If <var>current date</var> is less than the <var>timeout date</var> then continue to the step
  1438                   labeled <em>refresh subscription</em> above.
  1439                   </li>
  1440                   <li>Send a HTTP SUBSCRIBE request with a <em>SID</em> header with the string value of <var>callback
  1441                   ID</var> and a user-agent defined <em>TIMEOUT</em> header (in the form <code>Second-XX</code> where
  1442                   <code>XX</code> is the user-agent defined timeout value in seconds) towards the <var>network service
  1443                   record</var>'s <code>eventsUrl</code> property.
  1444                   </li>
  1445                   <li>On receiving a valid 200 OK, update <var>callback ID</var> with the string value of the first
  1446                   included <em>SID</em> header and set <var>timeout date</var> to the sum of the current UTC date value
  1447                   plus the integer value of the first included <em>TIMEOUT</em> header (minus the leading string of
  1448                   <code>Second-</code>), if it exists. If the current date is greater than or equal to <var>timeout
  1449                   date</var> then the <a>user agent</a> SHOULD continue from the step labeled <em>refresh
  1450                   subscription</em> above. For all non 200 OK responses the <a>user agent</a> SHOULD continue from the
  1451                   step labeled <em>refresh subscription</em> above.
  1452                   </li>
  1453                 </ol>
  1454               </li>
  1455               <li>
  1456                 <em>Listen</em>: For each HTTP NOTIFY request received at the <var>callback URL</var> the <a>user
  1457                 agent</a> is to run the following steps:
  1458                 <ol class="rule">
  1459                   <li>Let <var>content clone</var> be the result of obtaining the message body of the HTTP NOTIFY
  1460                   request. If <var>content clone</var> is empty, then the <a>user agent</a> MUST abort these steps.
  1461                   </li>
  1462                   <li>Let <var>notification event</var> be a new simple event that uses the <a href=
  1463                   "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1464                         class="externalDFN"><code>Event</code></a> interface with the name <a href=
  1465                         "#event-notify"><code>notify</code></a>, which does not bubble, is not cancellable, and has no
  1466                         default action.
  1467                   </li>
  1468                   <li>Let the <code>data</code> attribute of <var>notification event</var> have the DOMString value of
  1469                   <var>content clone</var>.
  1470                   </li>
  1471                   <li>
  1472                     <a href="http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
  1473                         class="externalDFN">Queue a task</a> to dispatch <var>notification event</var> at the current
  1474                         <a><code>NetworkService</code></a> object.
  1475                   </li>
  1476                   <li>Return a HTTP 200 OK response to the sender of the HTTP NOTIFY request.
  1477                   </li>
  1478                 </ol>
  1479               </li>
  1480             </ol>
  1481           </li>
  1482         </ol>
  1483         <p>
  1484           A <a>user agent</a> can <dfn>terminate an existing UPnP Events Subscription</dfn> at any time for a
  1485           <var>network service record</var> by sending an HTTP UNSUBSCRIBE request - as defined in 'Section 4.1.4:
  1486           Cancelling a subscription with UNSUBSCRIBE' in [[!UPNP-DEVICEARCH11]] - with a HOST header set to that
  1487           <var>active service</var>'s <code>eventsUrl</code> property and a SID header set to the <var>callback
  1488           ID</var> obtained when the initial <a>setup a UPnP Events Subscription</a> action occurred.
  1489         </p>
  1490       </section>
  1491       <section>
  1492         <h5>
  1493           Discovery and Launch Protocol (<abbr title="Discovery and Launch Protocol">DIAL</abbr>)
  1494         </h5>
  1495         <p>
  1496           A user agent that implements DIAL service discovery MUST issue a <dfn>search request for DIAL-enabled
  1497           devices</dfn> against the user's current local network according to the full normative text and timing
  1498           provided in 'Section 1.3.2: Search request with M-SEARCH' detailed in [[!UPNP-DEVICEARCH11]].
  1499         </p>
  1500         <p>
  1501           Let <var>dial version</var> be the version number specified in the <a>valid service type</a> token. Let
  1502           <var>dial search target</var> be the concatentation of the
  1503           <code>urn:dial-multiscreen-org:service:dial:</code> string constant with the <var>dial version</var>
  1504           (currently, <var>dial version</var> can only be <code>1</code>)
  1505         </p>
  1506         <p>
  1507           The user agent MUST issue all <a title="search request for DIAL devices">search requests for DIAL devices</a>
  1508           with a HTTP request line equal to <code>M-SEARCH * HTTP/1.1</code>, with a HOST header equal to the reserved
  1509           multicast address and port of <code>239.255.255.250:1900</code>, a MAN header equal to
  1510           <code>ssdp:discover</code>, an ST header equal to <var>dial search target</var> and a user-agent defined MX
  1511           header equal to a <dfn>maximum DIAL advertisement response wait time</dfn> value between <code>1</code> and
  1512           <code>5</code> seconds.
  1513         </p>
  1514         <p>
  1515           The user agent MUST listen for any incoming responses to a <a>search request for DIAL devices</a>.
  1516         </p>
  1517         <p>
  1518           For each HTTP Response following an initial <a>search request for DIAL devices</a> sent on a <a>standard UPnP
  1519           address and port</a> the user agent MUST run the following steps:
  1520         </p>
  1521         <ol class="rule">
  1522           <li>If the HTTP Response is not a HTTP 200 OK response then this response is invalid and the user agent MUST
  1523           discard this response, abort any remaining steps and return. The user agent MAY issue a new <a>search request
  1524           for DIAL devices</a> as a result of this error occurring.
  1525           </li>
  1526           <li>If the <a>maximum DIAL advertisement response wait time</a> has been exceeded since the initial <a>search
  1527           request for DIAL devices</a> was sent then the <a>HTTP Response</a> is invalid and the user agent MUST
  1528           discard this response, abort any remaining steps and return. The user agent MAY stop listening for responses
  1529           from the current <a>search request for DIAL devices</a> as a result of this error occurring. Equally, the
  1530           user agent MAY issue a new <a>search request for DIAL devices</a> as a result of this error occurring.
  1531           </li>
  1532           <li>Let <var>dial device</var> be an Object with a property for each HTTP header received in the <a>HTTP
  1533           Response</a>, with each key being the name of a HTTP response header and each value being that HTTP response
  1534           header's value.
  1535           </li>
  1536           <li>If <var>dial device</var> does not contain at least one <var>CACHE-CONTROL</var> entry, at least one
  1537           <var>USN</var> entry, at least one <var>ST</var> entry and at least one <var>LOCATION</var> entry or the
  1538           value of its <var>ST</var> entry is not <var>dial search target</var>, then the <a>HTTP Response</a> is
  1539           invalid and the <a>user agent</a> MUST discard this response, abort any remaining steps and return.
  1540           </li>
  1541           <li>The user agent MUST run the rule for <a>obtaining a UPnP Device Description File</a> passing in the first
  1542           occurrence of <var>LOCATION</var> from <var>dial device</var> as the <var>device descriptor URL</var>
  1543           argument and the first occurrence of <var>USN</var> from <var>dial device</var> as the <var>device
  1544           identifier</var> argument and the first occurrence of <var>CACHE-CONTROL</var> from <var>dial device</var>
  1545           (minus the leading string of <code>max-age=</code>) as the <var>device expiry</var> argument.
  1546           </li>
  1547         </ol>
  1548         <p>
  1549           The rule for <dfn>obtaining a DIAL Device Description File</dfn> is the process of obtaining the contents of
  1550           a standard UPnP Device Description [[!UPNP-DEVICEARCH11]] from a URL-based resource. This rule takes three
  1551           arguments - <var>device descriptor URL</var>, <var>device identifier</var> and <var>device expiry</var> - and
  1552           when called the user agent MUST run the following steps:
  1553         </p>
  1554         <ol class="rule">
  1555           <li>Let <var>device descriptor file</var> contain the contents of the file located at the URL provided in
  1556           <var>device descriptor URL</var> obtained according to the rules defined in 'Section 2.11: Retrieving a
  1557           description using HTTP' in [[!UPNP-DEVICEARCH11]].
  1558           </li>
  1559           <li>Let <var>application url</var> be the value of the first occurrence of the <code>Application-URL</code>
  1560           response header field obtained according to the rules defined in 'Section 5.4: Device Description Response'
  1561           in [<a href="https://sites.google.com/a/dial-multiscreen.org/dial/dial-protocol-specification">DIAL</a>]
  1562           </li>
  1563           <li>If the value provided in <var>device descriptor URL</var> cannot be resolved as a reachable URL on the
  1564           current network or the <var>device descriptor file</var> remains empty or <var>application url</var> is
  1565           undefined then it is invalid and the <a>user agent</a> MUST abort any remaining steps and return.
  1566           </li>
  1567           <li>Run the following steps to add the newly discovered DIAL service:
  1568             <ol class="rule">
  1569               <li>Let <var>network service record</var> be a new Object consisting of the following empty properties:
  1570               <code>id</code>, <code>deviceId</code>, <code>name</code>, <code>type</code>, <code>url</code>,
  1571               <code>expiryTimestamp</code>.
  1572               </li>
  1573               <li>Set <var>network service record</var>'s <code>id</code> property to the first occurrence of the
  1574               <code>&lt;UDN&gt;</code> element in the <var>descriptor file</var> prefixed with the <code>dial:</code>
  1575               string constant
  1576               </li>
  1577               <li>Set <var>network service record</var>'s <code>deviceId</code> property to the value of <var>device
  1578               identifier</var>.
  1579               </li>
  1580               <li>Set <var>network service record</var>'s <code>name</code> property to the string value of the first
  1581               occurrence of the <code>&lt;friendlyName&gt;</code> element in the <var>descriptor file</var>.
  1582               </li>
  1583               <li>Set <var>network service record</var>'s <code>type</code> property to <var>dial search target</var>.
  1584               </li>
  1585               <li>Set <var>network service record</var>'s <code>url</code> property to the string value of the
  1586               <var>application url</var>.
  1587               </li>
  1588               <li>Set <var>network service record</var>'s <code>expiryTimestamp</code> property to the value of the
  1589               current date, in UTC timestamp format, plus the value of <var>device expiry</var>.
  1590               </li>
  1591               <li>Run the general rule for <a>adding an available service</a>, passing in the current <var>network
  1592               service record</var> as the only argument.
  1593               </li>
  1594             </ol>
  1595           </li>
  1596         </ol>
  1597       </section>
  1598       <section>
  1599         <h3>
  1600           Network Topology Monitoring
  1601         </h3>
  1602         <div>
  1603           <p>
  1604             When the <a>user agent</a> detects that the user has dropped from a connected network then, for each
  1605             <var>existing service record</var> in the <a>list of available service records</a> discovered via that
  1606             network connection, the <a>user agent</a> MUST run the general rule for <a>removing an available
  1607             service</a> passing in each <var>existing service record</var>'s <code>id</code> property as the only
  1608             argument for each call.
  1609           </p>
  1610           <p>
  1611             When the <a>user agent</a> detects that the user has connected to a new network or reconnected to an
  1612             existing network, then it SHOULD restart its discovery mechanisms as defined in the <a href=
  1613             "#service-discovery">Service Discovery</a> section of this specification, maintaining the existing <a>list
  1614             of active service managers</a> currently in use.
  1615           </p>
  1616         </div>
  1617       </section>
  1618     </section>
  1619     <section>
  1620       <h3>
  1621         Events Summary
  1622       </h3>
  1623       <p>
  1624         The following events are dispatched on the <a href="#networkservices"><code>NetworkServices</code></a> and/or
  1625         <a href="#networkservice"><code>NetworkService</code></a> objects:
  1626       </p>
  1627       <table border="1">
  1628         <thead>
  1629           <tr>
  1630             <th>
  1631               <span>Event name</span>
  1632             </th>
  1633             <th>
  1634               <span>Interface</span>
  1635             </th>
  1636             <th>
  1637               <span>Dispatched when...</span>
  1638             </th>
  1639           </tr>
  1640         </thead>
  1641         <tbody>
  1642           <tr>
  1643             <td>
  1644               <dfn id="event-serviceavailable"><code>serviceavailable</code></dfn>
  1645             </td>
  1646             <td>
  1647               <a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1648                   class="externalDFN"><code>Event</code></a>
  1649             </td>
  1650             <td>
  1651               When a new service that matches one of the <a>requested type tokens</a> is found in the current network.
  1652             </td>
  1653           </tr>
  1654           <tr>
  1655             <td>
  1656               <dfn id="event-serviceunavailable"><code>serviceunavailable</code></dfn>
  1657             </td>
  1658             <td>
  1659               <a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1660                   class="externalDFN"><code>Event</code></a>
  1661             </td>
  1662             <td>
  1663               When an existing service that matches one of the <a>requested type tokens</a> gracefully leaves or
  1664               expires from the current network.
  1665             </td>
  1666           </tr>
  1667           <tr>
  1668             <td>
  1669               <dfn id="event-serviceonline"><code>serviceonline</code></dfn>
  1670             </td>
  1671             <td>
  1672               <a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1673                   class="externalDFN"><code>Event</code></a>
  1674             </td>
  1675             <td>
  1676               When a current service renews its service registration within the current network.
  1677             </td>
  1678           </tr>
  1679           <tr>
  1680             <td>
  1681               <dfn id="event-serviceoffline"><code>serviceoffline</code></dfn>
  1682             </td>
  1683             <td>
  1684               <a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1685                   class="externalDFN"><code>Event</code></a>
  1686             </td>
  1687             <td>
  1688               When a current service gracefully leaves or otherwise expires from the current network.
  1689             </td>
  1690           </tr>
  1691           <tr>
  1692             <td>
  1693               <dfn id="event-notify"><code>notify</code></dfn>
  1694             </td>
  1695             <td>
  1696               <a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1697                   class="externalDFN"><code>Event</code></a>
  1698             </td>
  1699             <td>
  1700               When a valid UPnP Events Subscription Message is received on a <a>user-agent generated callback url</a>
  1701               for a current service. This event never fires for Zeroconf-based services.
  1702             </td>
  1703           </tr>
  1704         </tbody>
  1705       </table>
  1706     </section>
  1707     <section>
  1708       <h3>
  1709         Garbage collection
  1710       </h3>
  1711       <p>
  1712         A user agent MUST only garbage collect a <a><code>NetworkServices</code></a> object and remove its entry from
  1713         the <a>list of active service managers</a> when the user has navigated away from the <a href=
  1714         "http://www.whatwg.org/specs/web-apps/current-work/complete/browsers.html#entry-script"
  1715            class="externalDFN">entry script</a>'s <a href=
  1716            "http://www.whatwg.org/specs/web-apps/current-work/complete/origin-0.html#origin"
  1717            class="externalDFN">origin</a> in which the current <a><code>NetworkServices</code></a> object was provided.
  1718       </p>
  1719       <p>
  1720         A user agent MUST NOT garbage collect individual <a><code>NetworkService</code></a> objects until their parent
  1721         <a><code>NetworkServices</code></a> object has been garbage collected.
  1722       </p>
  1723       <p>
  1724         A user agent MUST garbage collect the <a><code>NetworkService</code></a> <a>indexed properties</a> of a
  1725         <a><code>NetworkServices</code></a> object when that <a><code>NetworkServices</code></a> object itself has been
  1726         garbage-collected.
  1727       </p>
  1728     </section>
  1729     <section>
  1730       <h3>
  1731         Use Cases and Requirements
  1732       </h3>
  1733       <p>
  1734         This section covers what the requirements are for this API, as well as illustrates some use cases.
  1735       </p>
  1736       <ul class="rule">
  1737         <li>Once a user has given permission, user agents should provide the ability for Web pages to communicate
  1738         directly with a Local-networked Service.
  1739           <ul class="rule">
  1740             <li>Example: A web-based TV remote control. A Web page wants to control the current user's TV, changing the
  1741             programming shown or increasing/decreasing/muting the volume of the Local-networked Device. The Web page
  1742             requests a service type that is known to be implemented by television sets to which it has the application
  1743             logic to communicate. Local devices providing the request service types are discovered and presented to the
  1744             user for authorization. The user selects one or more of the discovered television sets to be accessible to
  1745             the current Web page and then clicks 'Share'. The Web page can now communicate directly with the
  1746             user-authorized Local-networked services.
  1747             </li>
  1748           </ul>
  1749         </li>
  1750         <li>Web pages should be able to communicate with Local-networked Services using the messaging channel supported
  1751         by those Devices.
  1752           <ul class="rule">
  1753             <li>Example: A Web page advertises that it is capable of controlling multiple Home Media Servers. The user
  1754             can select their Home Media Server type from a drop-down list, at which point the Web page sends a request
  1755             to the user agent to connect with the associated service type of the Home Media Server. The Media Server
  1756             selected implements a Web Socket channel for bi-directional service communication and so the Web page opens
  1757             a web socket to the requested Media Server and can communicate as required via that appropriate channel.
  1758             </li>
  1759           </ul>
  1760         </li>
  1761         <li>Web pages should be able to communicate with Local-networked Services using the messaging format supported
  1762         by those Devices.
  1763           <ul class="rule">
  1764             <li>Example: A Web page advertises that it is capable of interacting with and controlling multiple types of
  1765             Home Media Server. The user can select their Home Media Server type from a drop-down list or known Media
  1766             Servers, at which point the Web page sends a request to the user agent to connect with the associated
  1767             service type (and, optionally, the associated event type) of the Home Media Server. The communication
  1768             protocols supported by Home Media Servers typically vary between UPnP, JSON-RPC, Protocol Buffers or other
  1769             messaging formats depending on the Home Media Server requested. The Web page is able to communicate with
  1770             the user-selected Home Media Server in the messaging format supported by that Device, which, in this
  1771             example is a simple key/value pair text format.
  1772             </li>
  1773           </ul>
  1774         </li>
  1775         <li>Web pages should not be able to communicate with Local-networked Services that have not been authorized by
  1776         the user thereby maintaining the user's privacy.
  1777           <ul class="rule">
  1778             <li>Example: A Web page requests access to one type of Local-networked service. The user authorizes access
  1779             to that particular service. Other services running on that same device, and on other devices within the
  1780             network, should not be accessible to the current Web page.
  1781             </li>
  1782           </ul>
  1783         </li>
  1784         <li>A user should be able to share one or more Local-networked Services based on a particular service type
  1785         request from a Web page.
  1786           <ul class="rule">
  1787             <li>Example: A Web page is capable of interacting with a specific profile of Local-networked Service. As
  1788             such, it makes a request to the user agent to access those services, of which multiple matches are found.
  1789             The user is capable of selecting one or more of the discovered services to share with the Web page. The Web
  1790             page can then implement a drag-and-drop interface for the user to drag specific actions on to one or more
  1791             of the authorized Local-networked Services.
  1792             </li>
  1793           </ul>
  1794         </li>
  1795         <li>User agents should provide an API exposed to script that exposes the features above. The user is notified
  1796         by UI anytime interaction with Local-networked Services is requested, giving the user full ability to cancel or
  1797         abort the transaction. The user selects the Local-networked Services to be connected to the current Web page,
  1798         and can cancel these at any time. No invocations to these APIs occur silently without user intervention.
  1799         </li>
  1800       </ul>
  1801     </section>
  1802     <section class="informative appendix">
  1803       <h3>
  1804         Examples
  1805       </h3>
  1806       <div class="example">
  1807         <p>
  1808           This sample code exposes a button. When clicked, this button is disabled and the user is prompted to offer a
  1809           network service. The user may also select multiple network services. When the user has authorized a network
  1810           service to be connected to the web page then the web page issues a simple command to get a list of all the
  1811           albums stored on the connected media player service.
  1812         </p>
  1813         <p>
  1814           The button is re-enabled only when the connected network service disconnects for whatever reason (the service
  1815           becomes unavailable on the network, the user disconnects from their current network or the user revokes
  1816           access to the service from the current web page). At this point the user can re-click the button to select a
  1817           new network service to connect to the web page and the above steps are repeated.
  1818         </p>
  1819         <p>
  1820           The provided service type identifier and service interaction used in this example is based on the
  1821           well-defined service type and messaging format supported by the <a href="http://xbmc.org/about/">XBMC Media
  1822           Server</a>.
  1823         </p>
  1824         <hr>
  1825         <pre class="highlight">
  1826 &lt;input type="button" value="Start" onclick="start()" id="startBtn"/&gt;
  1827 &lt;div id="debugconsole"&gt;&lt;/div&gt;
  1828 
  1829 &lt;script&gt;
  1830  var startBtn = document.getElementById('startBtn'),
  1831      debug = document.getElementById('debugconsole');
  1832 
  1833  function start() {
  1834    if(navigator.getNetworkServices) {
  1835       navigator.getNetworkServices('zeroconf:_xbmc-jsonrpc._tcp', gotXBMCService, error);
  1836       startBtn.disabled = true;
  1837    } else {
  1838       debug.innerHTML += "&lt;br&gt;Service Discovery not supported!";
  1839    }
  1840  }
  1841 
  1842  function gotXBMCService(services) {
  1843 
  1844 // Listen for service disconnect messages
  1845 
  1846    services[0].addEventListener('serviceoffline', function ( e ) {
  1847        debug.innerHTML += "&lt;br&gt;" + services[0].name + " disconnected.";
  1848        startBtn.disabled = false;
  1849    }, false);
  1850 
  1851 // Send a service message to get albums list (and process the service response)
  1852 
  1853    var svcXhr = new XMLHttpRequest();
  1854    svcXhr.open("POST", services[0].url + "/getAlbums"); // services[0].url and its sub-resources have been
  1855                                                         // whitelisted for cross-site XHR use in this
  1856                                                         // current browsing context.
  1857 
  1858    svcXhr.setRequestHeader('Content-Type', 'application/json-rpc');
  1859 
  1860    svcXhr.addEventListener('readystatechange', function ( response ) {
  1861      if( response.readyState != 4 || response.status != 200 )
  1862         return;
  1863      debug.innerHTML += "&lt;br&gt;" + services[0].name + " response received: ";
  1864      debug.textContent += JSON.parse(response.responseText);
  1865    }, false);
  1866 
  1867    var svcMsg = [
  1868      { "jsonrpc": "2.0", "method": "AudioLibrary.GetAlbums", "params": { "genreid": -1,
  1869          "artistid": -1, "start": -1, "end": -1 }, "id": "1" }
  1870    ];
  1871 
  1872    svcXhr.send(JSON.stringify(svcMsg));
  1873    debug.innerHTML += "&lt;br&gt;" + services[0].name + " request sent: ";
  1874    debug.textContent += JSON.stringify(svcMsg);
  1875 
  1876  }
  1877 
  1878  function error( err ) {
  1879    debug.innerHTML += "&lt;br&gt;An error occurred obtaining a local network service.";
  1880    startBtn.disabled = false;
  1881  }
  1882 &lt;/script&gt;
  1883 </pre>
  1884       </div>
  1885       <div class="example">
  1886         <p>
  1887           This sample exposes a drop-down list containing a number of common Home-based audio devices. When the user
  1888           selects an audio device from the list provided, they are prompted to authorize a network service based on the
  1889           service type requested. The user may also select multiple network services matching the selected service
  1890           type. In this example, the user selects their make as being <var>Sony</var> and their model as being
  1891           <var>Bravia S1000</var> from which the Web page can derive a service type
  1892           (<var>urn:schemas-upnp-org:service:RenderingControl:1</var>).<br>
  1893           <br>
  1894           Once the user has authorized the device, the web page sends a simple mute command according to the messaging
  1895           format supported by the device.
  1896         </p>
  1897         <hr>
  1898         <pre class="highlight">
  1899 &lt;select name="make" id="make"&gt;
  1900   &lt;option selected="selected" disabled="disabled"&gt;Select make&lt;/option&gt;
  1901   &lt;option&gt;Sony&lt;/option&gt;
  1902   &lt;option&gt;Philips&lt;/option&gt;
  1903   &lt;option&gt;Alba&lt;/option&gt;
  1904 &lt;/select&gt;
  1905 &lt;select name="model" id="model"&gt;&lt;/select&gt;
  1906 &lt;div id="debugconsole"&gt;&lt;/div&gt;
  1907 
  1908 &lt;script&gt;
  1909   var debug = document.getElementById('debugconsole');
  1910 
  1911   var models = {
  1912     "Sony": [
  1913       {"name": "Bravia TV S1000", "type": "upnp", "service": "urn:schemas-upnp-org:service:RenderingControl:1" },
  1914       {"name": "Bravia TV S2000", "type": "zeroconf", "service": "_mediarenderer._http._tcp" },
  1915       {"name": "HiFi WD10", "type": "upnp", "service": "urn:schemas-upnp-org:service:RenderingControl:1" }
  1916     ],
  1917     "Philips": [ /* ... */ ],
  1918     "Alba": [ /* ... */ ]
  1919   };
  1920 
  1921   var makeEl = document.getElementById("make"),
  1922       modelEl = document.getElementById("model");
  1923 
  1924   makeEl.addEventListener('change', function() {
  1925     modelEl.innerHTML = ""; // reset
  1926     var defaultOption = document.createElement("option");
  1927     defaultOption.textContent = "Select model";
  1928     defaultOption.setAttribute("disabled", "disabled");
  1929     defaultOption.setAttribute("selected", "selected");
  1930     modelEl.appendChild(defaultOption);
  1931     for(var i = 0, l = models[makeEl.value].length; i &lt; l; i++) {
  1932       var option = document.createElement("option");
  1933       option.textContent = models[makeEl.value][i]["name"];
  1934       option.setAttribute("value", models[makeEl.value][i]["type"] + ":" + models[makeEl.value][i]["service"]);
  1935       modelEl.appendChild(option);
  1936     }
  1937   }, false);
  1938 
  1939   modelEl.addEventListener('change', function() {
  1940     if(navigator.getNetworkServices &amp;&amp;
  1941          modelEl.value == "upnp:urn:schemas-upnp-org:service:RenderingControl:1") {
  1942       navigator.getNetworkServices(modelEl.value, successCallback, errorCallback);
  1943     } else if (modelEl.value == "zeroconf:_mediarenderer._http._tcp") {
  1944       debug.innerHTML += "&lt;br&gt;Service type is not implemented by this application.";
  1945     } else {
  1946       debug.innerHTML += "&lt;br&gt;Service Discovery is not supported!";
  1947     }
  1948   }, false);
  1949 &lt;/script&gt;
  1950 
  1951 &lt;script&gt;
  1952   function successCallback( services ) {
  1953 
  1954   // Listen for service push notification messages
  1955 
  1956     services[0].addEventListener('notify', function ( msg ) {
  1957          debug.innerHTML += "&lt;br&gt;" + services[0].name + " event received: ";
  1958          debug.textContent += msg.data;
  1959     }, false);
  1960 
  1961  // Send a control signal to mute the service audio
  1962 
  1963     var svcXhr = new XMLHttpRequest();
  1964     svcXhr.open("POST", services[0].url); // services[0].url and its
  1965                                           // sub-resources have been whitelisted for
  1966                                           // cross-site XHR use in this current
  1967                                           // browsing context.
  1968 
  1969     svcXhr.setRequestHeader('SOAPAction', 'urn:schemas-upnp-org:service:RenderingControl:1#SetMute');
  1970     svcXhr.setRequestHeader('Content-Type', 'text/xml; charset="utf-8";');
  1971 
  1972     svcXhr.onreadystatechange = function ( response ) {
  1973       if( response.readyState != 4 || response.status != 200 )
  1974         return;
  1975       debug.innerHTML += "&lt;br&gt;" + services[0].name + " response received: ";
  1976       debug.textContent += response.responseXML;
  1977     }
  1978 
  1979     // Service messaging to mute the provided service
  1980     var svcMsg = '&lt;?xml version="1.0" encoding="utf-8"?&gt;' +
  1981                  '&lt;s:Envelope s:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" ' +
  1982                    'xmlns:s="http://schemas.xmlsoap.org/soap/envelope/"&gt;' +
  1983                    '&lt;s:Body&gt;' +
  1984                      '&lt;u:SetMute xmlns:u="urn:schemas-upnp-org:service:RenderingControl:1"&gt;' +
  1985                        '&lt;InstanceID&gt;0&lt;/InstanceID&gt;' +
  1986                        '&lt;Channel&gt;Master&lt;/Channel&gt;' +
  1987                        '&lt;DesiredMute&gt;true&lt;/DesiredMute&gt;' +
  1988                      '&lt;/u:SetMute&gt;' +
  1989                    '&lt;/s:Body&gt;' +
  1990                  '&lt;/s:Envelope&gt;';
  1991 
  1992     svcXhr.send(svcMsg);
  1993     debug.innerHTML += "&lt;br&gt;" + services[0].name + " request sent: ";
  1994     debug.textContent += svcMsg;
  1995   }
  1996 
  1997   function errorCallback( error ) {
  1998     debug.innerHTML += "&lt;br&gt;An error occurred: " + error.code;
  1999   }
  2000 &lt;/script&gt;
  2001 </pre>
  2002       </div>
  2003     </section>
  2004     <section>
  2005       <h3>
  2006         Acknowledgements
  2007       </h3>
  2008       <p>
  2009         Thanks are expressed by the editor to the following individuals for their feedback on this specification to
  2010         date (in alphabetical order):<br>
  2011         <br>
  2012         Gar Bergstedt, Lars-Erik Bolstad, Cathy Chan, Hari G Kumar, Bob Lund, Giuseppe Pascale, Marcin Simonides,
  2013         Clarke Stevens, Christian Söderström, Mark Vickers.
  2014       </p>
  2015       <p>
  2016         Thanks are also expressed by the editor to the following organizations and groups for their support in
  2017         producing this specification to date (in alphabetical order):<br>
  2018         <br>
  2019         CableLabs, Opera Software ASA, W3C Device APIs Working Group, W3C Web and TV Interest Group.
  2020       </p>
  2021     </section>
  2022   </body>
  2023 </html>