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65 KiB
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</style><link href="http://www.w3.org/StyleSheets/TR/W3C-WD" rel="stylesheet" type="text/css"></head>
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<body><div class="head" id="head">
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<p><a href="http://www.w3.org/"><img alt="W3C" height="48" src="http://www.w3.org/Icons/w3c_home" width="72"></a></p>
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<h1>Server-Sent Events</h1>
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<h2 class="no-num no-toc" id="editor-s-draft-20-october-2011">W3C Working Draft 20 October 2011</h2>
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<dl>
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<dt>This Version:</dt>
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<dd><a href="http://www.w3.org/TR/2011/WD-eventsource-20111020/">http://www.w3.org/TR/2011/WD-eventsource-20111020/</a></dd>
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<dt>Latest Published Version:</dt>
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<dd><a href="http://www.w3.org/TR/eventsource/">http://www.w3.org/TR/eventsource/</a></dd>
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<dt>Latest Editor's Draft:</dt>
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<dd><a class="latest-link" href="http://dev.w3.org/html5/eventsource/">http://dev.w3.org/html5/eventsource/</a></dd>
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<dt>Previous Versions:</dt>
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<dd><a href="http://www.w3.org/TR/2011/WD-eventsource-20110310/">http://www.w3.org/TR/2011/WD-eventsource-20110310/</a></dd>
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<dd><a href="http://www.w3.org/TR/2011/WD-eventsource-20110208/">http://www.w3.org/TR/2011/WD-eventsource-20110208/</a></dd>
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<dd><a href="http://www.w3.org/TR/2009/WD-eventsource-20091222/">http://www.w3.org/TR/2009/WD-eventsource-20091222/</a></dd>
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<dd><a href="http://www.w3.org/TR/2009/WD-eventsource-20091029/">http://www.w3.org/TR/2009/WD-eventsource-20091029/</a></dd>
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<dd><a href="http://www.w3.org/TR/2009/WD-eventsource-20090423/">http://www.w3.org/TR/2009/WD-eventsource-20090423/</a></dd>
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<!-- :ZZZ -->
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<dt>Editor:</dt>
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<dd><a href="mailto:ian@hixie.ch">Ian Hickson</a>, Google, Inc.</dd>
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</dl><p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a>
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© 2011 <a href="http://www.w3.org/"><abbr title="World Wide
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Web Consortium">W3C</abbr></a><sup>®</sup> (<a href="http://www.csail.mit.edu/"><abbr title="Massachusetts
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Institute of Technology">MIT</abbr></a>, <a href="http://www.ercim.eu/"><abbr title="European Research
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Consortium for Informatics and Mathematics">ERCIM</abbr></a>, <a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C
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<a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
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<a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>
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and <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document
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use</a> rules apply.</p>
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<!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
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<p class="alt">The bulk of the text of this specification is also
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available in the WHATWG <a href="http://www.whatwg.org/specs/web-apps/current-work/complete.html#eventsource">Web Applications 1.0</a> specification, under a license that permits
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reuse of the specification text.</p>
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<!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
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</div><hr class="top"><h2 class="no-num no-toc" id="abstract">Abstract</h2><p>This specification defines an API for opening an HTTP connection
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for receiving push notifications from a server in the form of DOM
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events. The API is designed such that it can be extended to work
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with other push notification schemes such as Push SMS.<h2 class="no-num no-toc" id="status-of-this-document">Status of This document</h2><p><em>This section describes the status of this document at the
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time of its publication. Other documents may supersede this
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document. A list of current W3C publications and the
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latest <!-- DO NOT CHANGE THIS BACK TO THE STANDARD BOILERPLATE, AS IT IS INACCURATE -->
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revision of this technical report can be found in the <a href="http://www.w3.org/TR/">W3C technical reports index</a> at
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http://www.w3.org/TR/.</em></p><p>If you wish to make comments regarding this document in a manner
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that is tracked by the W3C, please submit them via using <a href="http://www.w3.org/Bugs/Public/enter_bug.cgi?product=HTML%20WG">our
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public bug database</a>. If you do not have an account then you can
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enter feedback using this form:<form action="http://www.whatwg.org/specs/web-apps/current-work/file-spam.cgi" method="post">
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<fieldset><legend>Feedback Comments</legend>
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<input name="id" type="hidden" value="top"><input name="component" type="hidden" value="Server-Sent Events (editor: Ian Hickson)"><input name="response" type="hidden" value="html"><p><label for="feedbackBox">Please enter your feedback, carefully
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indicating the title of the section for which you are submitting
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feedback, quoting the text that's wrong today if appropriate. If
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you're suggesting a new feature, it's really important to say
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<em>what</em> the problem you're trying to solve is. That's more
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important than the solution, in fact.</label></p>
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<p><textarea cols="79" id="feedbackBox" name="text" rows="10"></textarea></p>
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<p class="note">Please don't use section numbers as these tend to
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change rapidly and make your feedback harder to understand.</p>
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<script type="text/javascript">
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function checkFeedbackForm(form) {
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if (form.elements.text.value.match(/^ *</)) {
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alert('Please don\'t start your feedback with an angle bracket, instead explain what topic your feedback is about first.');
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return true;
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} else if (form.elements.text.value.match(/ [^ ]+ [^ ]+ [^ ]+ [^ ]+ /)) {
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if (form.elements.text.value.match(/^Please enter your feedback, carefully/)) {
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alert('Please enter your feedback, explaining what is wrong, and without repeating the instructions. Thanks!');
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return true;
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} else if (form.elements.text.value.match(/ [^ ]+ [^ ]+ [^ ]+ [^ ]+ /)) {
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form.action = "http://www.whatwg.org/specs/web-apps/current-work/file-bug.cgi";
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return true;
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} else {
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alert('Please include significantly more detail about exactly what problem you are trying to solve.');
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return false;
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}
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}
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}
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</script><p>
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<input onclick="return checkFeedbackForm(form)" type="submit" value="Submit feedback"><small>(Note: Your IP address and user agent will be publicly recorded for spam prevention purposes.)</small>
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</p>
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</fieldset></form><p>You can also e-mail feedback to <a href="mailto:public-webapps@w3.org">public-webapps@w3.org</a> (<a href="mailto:public-webapps-request@w3.org?subject=subscribe">subscribe</a>,
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<a href="http://lists.w3.org/Archives/Public/public-webapps/">archives</a>),
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or <a href="mailto:whatwg@whatwg.org">whatwg@whatwg.org</a> (<a href="http://lists.whatwg.org/listinfo.cgi/whatwg-whatwg.org">subscribe</a>,
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<a href="http://lists.whatwg.org/pipermail/whatwg-whatwg.org/">archives</a>).
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All feedback is welcome.</p><p>Implementors should be aware that this specification is not
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stable. <strong>Implementors who are not taking part in the
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discussions are likely to find the specification changing out from
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under them in incompatible ways.</strong> Vendors interested in
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implementing this specification before it eventually reaches the
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Candidate Recommendation stage should join the aforementioned
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mailing lists and take part in the discussions.<div id="multipage-common">
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</div><p>The latest
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stable version of the editor's draft of this specification is always
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available on <a href="http://dev.w3.org/html5/eventsource/">the W3C CVS server</a>
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and in the <a href="http://svn.whatwg.org/webapps/">WHATWG
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Subversion repository</a>. The <a href="http://www.whatwg.org/specs/web-apps/current-work/complete.html">latest
|
|
editor's working copy</a> (which may contain unfinished text in the
|
|
process of being prepared) contains the latest draft text of this
|
|
specification (amongst others). For more details, please see the <a href="http://wiki.whatwg.org/wiki/FAQ#What_are_the_various_versions_of_the_spec.3F">WHATWG
|
|
FAQ</a>.<p>Notifications of changes to this specification are sent along
|
|
with notifications of changes to related specifications using the
|
|
following mechanisms:<dl><dt>E-mail notifications of changes</dt>
|
|
<dd>Commit-Watchers mailing list (complete source diffs): <a href="http://lists.whatwg.org/listinfo.cgi/commit-watchers-whatwg.org">http://lists.whatwg.org/listinfo.cgi/commit-watchers-whatwg.org</a></dd>
|
|
<dt>Browsable version-control record of all changes:</dt>
|
|
<dd>CVSWeb interface with side-by-side diffs: <a href="http://dev.w3.org/cvsweb/html5/">http://dev.w3.org/cvsweb/html5/</a></dd>
|
|
<dd>Annotated summary with unified diffs: <a href="http://html5.org/tools/web-apps-tracker">http://html5.org/tools/web-apps-tracker</a></dd>
|
|
<dd>Raw Subversion interface: <code>svn checkout http://svn.whatwg.org/webapps/</code></dd>
|
|
</dl><p>The W3C <a href="http://www.w3.org/2008/webapps/">Web Applications
|
|
Working Group</a> is the W3C working group responsible for this
|
|
specification's progress along the W3C Recommendation track.
|
|
This specification is the 20 October 2011 Working Draft.
|
|
</p><p>Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.</p><p>This document was produced by a group operating under the <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5
|
|
February 2004 W3C Patent Policy</a>. W3C maintains a <a href="http://www.w3.org/2004/01/pp-impl/42538/status" rel="disclosure">public list of
|
|
any patent disclosures</a> made in connection with the deliverables
|
|
of the group; that page also includes instructions for disclosing a
|
|
patent. An individual who has actual knowledge of a patent which the
|
|
individual believes contains <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential
|
|
Claim(s)</a> must disclose the information in accordance with <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section
|
|
6 of the W3C Patent Policy</a>.<h2 class="no-num no-toc" id="contents">Table of Contents</h2>
|
|
<ol class="toc">
|
|
<li><a href="#server-sent-events-intro"><span class="secno">1 </span>Introduction</a></li>
|
|
<li><a href="#conformance-requirements"><span class="secno">2 </span>Conformance requirements</a>
|
|
<ol>
|
|
<li><a href="#dependencies"><span class="secno">2.1 </span>Dependencies</a></ol></li>
|
|
<li><a href="#terminology"><span class="secno">3 </span>Terminology</a></li>
|
|
<li><a href="#the-eventsource-interface"><span class="secno">4 </span>The <code>EventSource</code> interface</a></li>
|
|
<li><a href="#processing-model"><span class="secno">5 </span>Processing model</a></li>
|
|
<li><a href="#parsing-an-event-stream"><span class="secno">6 </span>Parsing an event stream</a></li>
|
|
<li><a href="#event-stream-interpretation"><span class="secno">7 </span>Interpreting an event stream</a></li>
|
|
<li><a href="#notes"><span class="secno">8 </span>Notes</a></li>
|
|
<li><a href="#eventsource-push"><span class="secno">9 </span>Connectionless push and other features</a></li>
|
|
<li><a href="#garbage-collection"><span class="secno">10 </span>Garbage collection</a></li>
|
|
<li><a href="#iana-considerations"><span class="secno">11 </span>IANA considerations</a>
|
|
<ol>
|
|
<li><a href="#text-event-stream"><span class="secno">11.1 </span><code>text/event-stream</code></a></li>
|
|
<li><a href="#last-event-id"><span class="secno">11.2 </span><code>Last-Event-ID</code></a></ol></li>
|
|
<li><a class="no-num" href="#references">References</a></li>
|
|
<li><a class="no-num" href="#acknowledgements">Acknowledgements</a></ol>
|
|
<hr><h2 id="server-sent-events-intro"><span class="secno">1 </span>Introduction</h2><p><i>This section is non-normative.</i><p>To enable servers to push data to Web pages over HTTP or using
|
|
dedicated server-push protocols, this specification introduces the
|
|
<code><a href="#eventsource">EventSource</a></code> interface.<p>Using this API consists of creating an <code><a href="#eventsource">EventSource</a></code>
|
|
object and registering an event listener.<pre>var source = new EventSource('updates.cgi');
|
|
source.onmessage = function (event) {
|
|
alert(event.data);
|
|
};</pre><p>On the server-side, the script ("<code title="">updates.cgi</code>" in this case) sends messages in the
|
|
following form, with the <code><a href="#text-event-stream">text/event-stream</a></code> MIME
|
|
type:<pre>data: This is the first message.
|
|
|
|
data: This is the second message, it
|
|
data: has two lines.
|
|
|
|
data: This is the third message.</pre><hr><p>Authors can separate events by using different event types. Here
|
|
is a stream that has two event types, "add" and "remove":<pre>event: add
|
|
data: 73857293
|
|
|
|
event: remove
|
|
data: 2153
|
|
|
|
event: add
|
|
|
|
data: 113411</pre><p>The script to handle such a stream would look like this (where
|
|
<code title="">addHandler</code> and <code title="">removeHandler</code> are functions that take one argument,
|
|
the event):<pre>var source = new EventSource('updates.cgi');
|
|
source.addEventListener('add', addHandler, false);
|
|
source.addEventListener('remove', removeHandler, false);</pre><p>The default event type is "message".<hr><p>Event streams requests can be redirected using HTTP 301 and 307
|
|
redirects as with normal HTTP requests. Clients will reconnect if
|
|
the connection is closed; a client can be told to stop reconnecting
|
|
using the HTTP 204 No Content response code.<p>Using this API rather than emulating it using
|
|
<code>XMLHttpRequest</code> or an <code>iframe</code> allows the
|
|
user agent to make better use of network resources in cases where
|
|
the user agent implementor and the network operator are able to
|
|
coordinate in advance. Amongst other benefits, this can result in
|
|
significant savings in battery life on portable devices. This is
|
|
discussed further in the section below on <a href="#eventsource-push">connectionless push</a>.<h2 id="conformance-requirements"><span class="secno">2 </span>Conformance requirements</h2><p>All diagrams, examples, and notes in this specification are
|
|
non-normative, as are all sections explicitly marked non-normative.
|
|
Everything else in this specification is normative.<p>The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
|
|
"OPTIONAL" in the normative parts of this document are to be
|
|
interpreted as described in RFC2119. For readability, these words do
|
|
not appear in all uppercase letters in this specification. <a href="#refsRFC2119">[RFC2119]</a><p>Requirements phrased in the imperative as part of algorithms
|
|
(such as "strip any leading space characters" or "return false and
|
|
abort these steps") are to be interpreted with the meaning of the
|
|
key word ("must", "should", "may", etc) used in introducing the
|
|
algorithm.<p>Some conformance requirements are phrased as requirements on
|
|
attributes, methods or objects. Such requirements are to be
|
|
interpreted as requirements on user agents.<p>Conformance requirements phrased as algorithms or specific steps
|
|
may be implemented in any manner, so long as the end result is
|
|
equivalent. (In particular, the algorithms defined in this
|
|
specification are intended to be easy to follow, and not intended to
|
|
be performant.)<p>The only conformance class defined by this specification is user
|
|
agents.<p>User agents may impose implementation-specific limits on
|
|
otherwise unconstrained inputs, e.g. to prevent denial of service
|
|
attacks, to guard against running out of memory, or to work around
|
|
platform-specific limitations.<p>When support for a feature is disabled (e.g. as an emergency
|
|
measure to mitigate a security problem, or to aid in development, or
|
|
for performance reasons), user agents must act as if they had no
|
|
support for the feature whatsoever, and as if the feature was not
|
|
mentioned in this specification. For example, if a particular
|
|
feature is accessed via an attribute in a Web IDL interface, the
|
|
attribute itself would be omitted from the objects that implement
|
|
that interface — leaving the attribute on the object but
|
|
making it return null or throw an exception is insufficient.<h3 id="dependencies"><span class="secno">2.1 </span>Dependencies</h3><p>This specification relies on several other underlying
|
|
specifications.<dl><dt>HTML</dt>
|
|
|
|
<dd>
|
|
|
|
<p>Many fundamental concepts from HTML are used by this
|
|
specification. <a href="#refsHTML">[HTML]</a></p>
|
|
|
|
</dd>
|
|
|
|
<dt>WebIDL</dt>
|
|
|
|
<dd>
|
|
|
|
<p>The IDL blocks in this specification use the semantics of the
|
|
WebIDL specification. <a href="#refsWEBIDL">[WEBIDL]</a></p>
|
|
|
|
</dd>
|
|
|
|
</dl><h2 id="terminology"><span class="secno">3 </span>Terminology</h2><p>The construction "a <code title="">Foo</code> object", where
|
|
<code title="">Foo</code> is actually an interface, is sometimes
|
|
used instead of the more accurate "an object implementing the
|
|
interface <code title="">Foo</code>".<p>The term DOM is used to refer to the API set made available to
|
|
scripts in Web applications, and does not necessarily imply the
|
|
existence of an actual <code>Document</code> object or of any other
|
|
<code>Node</code> objects as defined in the DOM Core
|
|
specifications. <a href="#refsDOMCORE">[DOMCORE]</a><p>An IDL attribute is said to be <em>getting</em> when its value is
|
|
being retrieved (e.g. by author script), and is said to be
|
|
<em>setting</em> when a new value is assigned to it.<h2 id="the-eventsource-interface"><span class="secno">4 </span>The <code><a href="#eventsource">EventSource</a></code> interface</h2><pre class="idl">[<a href="#dom-eventsource" title="dom-EventSource">Constructor</a>(DOMString url)]
|
|
interface <dfn id="eventsource">EventSource</dfn> : <span>EventTarget</span> {
|
|
readonly attribute DOMString <a href="#dom-eventsource-url" title="dom-EventSource-url">url</a>;
|
|
|
|
// ready state
|
|
const unsigned short <a href="#dom-eventsource-connecting" title="dom-EventSource-CONNECTING">CONNECTING</a> = 0;
|
|
const unsigned short <a href="#dom-eventsource-open" title="dom-EventSource-OPEN">OPEN</a> = 1;
|
|
const unsigned short <a href="#dom-eventsource-closed" title="dom-EventSource-CLOSED">CLOSED</a> = 2;
|
|
readonly attribute unsigned short <a href="#dom-eventsource-readystate" title="dom-EventSource-readyState">readyState</a>;
|
|
|
|
// networking
|
|
[TreatNonCallableAsNull] attribute <span>Function</span>? <a href="#handler-eventsource-onopen" title="handler-EventSource-onopen">onopen</a>;
|
|
[TreatNonCallableAsNull] attribute <span>Function</span>? <a href="#handler-eventsource-onmessage" title="handler-EventSource-onmessage">onmessage</a>;
|
|
[TreatNonCallableAsNull] attribute <span>Function</span>? <a href="#handler-eventsource-onerror" title="handler-EventSource-onerror">onerror</a>;
|
|
void <a href="#dom-eventsource-close" title="dom-EventSource-close">close</a>();
|
|
};</pre><p>The <dfn id="dom-eventsource" title="dom-EventSource"><code>EventSource(<var title="">url</var>)</code></dfn> constructor takes one argument,
|
|
<var title="">url</var>, which specifies the <span>URL</span> to
|
|
which to connect. When the <code>EventSource()</code> constructor is
|
|
invoked, the UA must run these steps:<ol><li><p><span title="resolve a url">Resolve</span> the
|
|
<span>URL</span> specified in <var title="">url</var>, relative to
|
|
the <span>entry script</span>'s <span title="script's base
|
|
URL">base URL</span>.</li>
|
|
|
|
<li><p>If the previous step failed, then throw a
|
|
<code>SyntaxError</code> exception.</li>
|
|
|
|
<li><p>Return a new <code><a href="#eventsource">EventSource</a></code> object, and continue
|
|
these steps in the background (without blocking scripts).</li>
|
|
|
|
<li>
|
|
|
|
<p>Do a <span>potentially CORS-enabled fetch</span> of the
|
|
resulting <span>absolute URL</span>, with the <i>mode</i> being
|
|
<span title="attr-crossorigin-use-credentials">Use
|
|
Credentials</span>, and the <i title="">origin</i> being the <span>entry
|
|
script</span>'s <span>origin</span>, and process the resource obtained in
|
|
this fashion, if any, as described below.</p>
|
|
|
|
<p class="note">The definition of the <span title="fetch">fetching</span> algorithm (which is used by CORS) is
|
|
such that if the browser is already fetching the resource
|
|
identified by the given <span>absolute URL</span>, that connection
|
|
can be reused, instead of a new connection being established. All
|
|
messages received up to this point are dispatched immediately, in
|
|
this case.</p>
|
|
|
|
</li>
|
|
|
|
</ol><p>This constructor must be visible when the <span>script's global
|
|
object</span> is either a <code>Window</code> object or an object
|
|
implementing the <code>WorkerUtils</code> interface.<hr><p>The <dfn id="dom-eventsource-url" title="dom-EventSource-url"><code>url</code></dfn>
|
|
attribute must return the <span>absolute URL</span> that resulted
|
|
from <span title="resolve a url">resolving</span> the value that was
|
|
passed to the constructor.</p><p>The <dfn id="dom-eventsource-readystate" title="dom-EventSource-readyState"><code>readyState</code></dfn>
|
|
attribute represents the state of the connection. It can have the
|
|
following values:<dl><dt><dfn id="dom-eventsource-connecting" title="dom-EventSource-CONNECTING"><code>CONNECTING</code></dfn> (numeric value 0)</dt>
|
|
|
|
<dd>The connection has not yet been established, or it was closed
|
|
and the user agent is reconnecting.</dd>
|
|
|
|
<dt><dfn id="dom-eventsource-open" title="dom-EventSource-OPEN"><code>OPEN</code></dfn> (numeric value 1)</dt>
|
|
|
|
<dd>The user agent has an open connection and is dispatching events
|
|
as it receives them.</dd>
|
|
|
|
<dt><dfn id="dom-eventsource-closed" title="dom-EventSource-CLOSED"><code>CLOSED</code></dfn> (numeric value 2)</dt>
|
|
|
|
<dd>The connection is not open, and the user agent is not trying to
|
|
reconnect. Either there was a fatal error or the <code title="dom-EventSource-close"><a href="#dom-eventsource-close">close()</a></code> method was
|
|
invoked.</dd>
|
|
|
|
</dl><p>When the object is created its <code title="dom-EventSource-readyState"><a href="#dom-eventsource-readystate">readyState</a></code> must be set to
|
|
<code title="dom-EventSource-CONNECTING"><a href="#dom-eventsource-connecting">CONNECTING</a></code> (0). The
|
|
rules given below for handling the connection define when the value
|
|
changes.<p>The <dfn id="dom-eventsource-close" title="dom-EventSource-close"><code>close()</code></dfn>
|
|
method must abort any instances of the <span>fetch</span> algorithm
|
|
started for this <code><a href="#eventsource">EventSource</a></code> object, and must set the
|
|
<code title="dom-EventSource-readyState"><a href="#dom-eventsource-readystate">readyState</a></code> attribute
|
|
to <code title="dom-EventSource-CLOSED"><a href="#dom-eventsource-closed">CLOSED</a></code>.</p><p>The following are the <span>event handlers</span> (and their
|
|
corresponding <span title="event handler event type">event handler
|
|
event types</span>) that must be supported, as IDL attributes, by
|
|
all objects implementing the <code><a href="#eventsource">EventSource</a></code> interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
|
|
<tbody><tr><td><dfn id="handler-eventsource-onopen" title="handler-EventSource-onopen"><code>onopen</code></dfn> <td> <code title="event-open">open</code>
|
|
<tr><td><dfn id="handler-eventsource-onmessage" title="handler-EventSource-onmessage"><code>onmessage</code></dfn> <td> <code title="event-message">message</code>
|
|
<tr><td><dfn id="handler-eventsource-onerror" title="handler-EventSource-onerror"><code>onerror</code></dfn> <td> <code title="event-error">error</code>
|
|
</table><hr><p>In addition to the above, each <code><a href="#eventsource">EventSource</a></code> object
|
|
has the following associated with it:<ul><li>A <dfn id="concept-event-stream-reconnection-time" title="concept-event-stream-reconnection-time">reconnection
|
|
time</dfn>, in milliseconds. This must initially be a
|
|
user-agent-defined value, probably in the region of a few
|
|
seconds.</li>
|
|
|
|
<li>A <dfn id="concept-event-stream-last-event-id" title="concept-event-stream-last-event-id">last event
|
|
ID string</dfn>. This must initially be the empty string.</li>
|
|
|
|
</ul><p>These values are not currently exposed on the interface.<h2 id="processing-model"><span class="secno">5 </span>Processing model</h2><p>The resource indicated in the argument to the <code title="dom-EventSource"><a href="#dom-eventsource">EventSource</a></code> constructor is <span title="fetch">fetched</span> when the constructor is run.<p>For HTTP connections, the <code title="">Accept</code> header may
|
|
be included; if included, it must contain only formats of event
|
|
framing that are supported by the user agent (one of which must be
|
|
<code><a href="#text-event-stream">text/event-stream</a></code>, as described below).<p>If the event source's <a href="#concept-event-stream-last-event-id" title="concept-event-stream-last-event-id">last event ID
|
|
string</a> is not the empty string, then a <code title="http-last-event-id"><a href="#last-event-id">Last-Event-ID</a></code> HTTP header must be
|
|
included with the request, whose value is the value of the event
|
|
source's <a href="#concept-event-stream-last-event-id" title="concept-event-stream-last-event-id">last event
|
|
ID string</a>, encoded as UTF-8.<p>User agents should use the <code>Cache-Control: no-cache</code>
|
|
header in requests to bypass any caches for requests of event
|
|
sources. (This header is not a <span title="custom request
|
|
headers">custom request header</span>, so the user agent will still
|
|
use the CORS <span>simple cross-origin request</span> mechanism.)
|
|
User agents should ignore HTTP cache headers in the response, never
|
|
caching event sources.<hr><p>As data is received, the <span title="concept-task">tasks</span>
|
|
queued by the <span>networking task source</span> to handle the data
|
|
must act as follows.<p>HTTP 200 OK responses with a <span>Content-Type</span> header
|
|
specifying the type <code><a href="#text-event-stream">text/event-stream</a></code>, either with no
|
|
parameters or with a single parameter with the name "<code title="">charset</code>" whose value is an <span>ASCII
|
|
case-insensitive</span> match for the string "<code title="">utf-8</code>", must be processed line by line <a href="#event-stream-interpretation">as described below</a>.<p>When a successful response with a supported <span>MIME
|
|
type</span> is received, such that the user agent begins parsing the
|
|
contents of the stream, the user agent must <a href="#announce-the-connection">announce the
|
|
connection</a>.<p>The <span title="concept-task">task</span> that the
|
|
<span>networking task source</span> places on the <span>task
|
|
queue</span> once the <span title="fetch">fetching algorithm</span>
|
|
for such a resource (with the correct <span>MIME type</span>) has
|
|
completed must <a href="#reestablish-the-connection">reestablish the connection</a>. This applies
|
|
whether the connection is closed gracefully or unexpectedly. It
|
|
doesn't apply for the error conditions listed below.<p>HTTP 200 OK responses that have a <span>Content-Type</span>
|
|
specifying an unsupported type (including the
|
|
<code><a href="#text-event-stream">text/event-stream</a></code> type with unsupported parameters or
|
|
parameters with unsupported values), or that have no
|
|
<span>Content-Type</span> at all, must cause the user agent to
|
|
<a href="#fail-the-connection">fail the connection</a>.</p><p>HTTP 305 Use Proxy, HTTP 401 Unauthorized, and 407 Proxy
|
|
Authentication Required should be treated transparently as for any
|
|
other subresource.<p>HTTP 301 Moved Permanently, HTTP 302 Found, 303 See Other, and
|
|
307 Temporary Redirect responses are handled by the <span title="fetch">fetching</span> and CORS algorithms. In the case of
|
|
301 redirects, the user agent must also remember the new URL so that
|
|
subsequent requests for this resource for this
|
|
<code><a href="#eventsource">EventSource</a></code> object start with the URL given for the
|
|
last 301 seen for requests for this object.<p>Any other HTTP response code not listed here, and any network
|
|
error that prevents the HTTP connection from being established in
|
|
the first place (e.g. DNS errors), must cause the user agent to
|
|
<a href="#fail-the-connection">fail the connection</a>.</p><p>For non-HTTP protocols, UAs should act in equivalent ways.<hr><p>When a user agent is to <dfn id="announce-the-connection">announce the connection</dfn>, the
|
|
user agent must <span>queue a task</span> to set the <code title="dom-EventSource-readyState"><a href="#dom-eventsource-readystate">readyState</a></code> attribute to
|
|
<code title="dom-EventSource-OPEN"><a href="#dom-eventsource-open">OPEN</a></code> and <span>fire a
|
|
simple event</span> named <code title="event-open">open</code> at
|
|
the <code><a href="#eventsource">EventSource</a></code> object.<p>When a user agent is to <dfn id="reestablish-the-connection">reestablish the connection</dfn>,
|
|
the user agent must <span>queue a task</span> to set the <code title="dom-EventSource-readyState"><a href="#dom-eventsource-readystate">readyState</a></code> attribute to
|
|
<code title="dom-EventSource-CONNECTING"><a href="#dom-eventsource-connecting">CONNECTING</a></code> and
|
|
<span>fire a simple event</span> named <code title="event-error">error</code> at the <code><a href="#eventsource">EventSource</a></code>
|
|
object, and then, after a delay equal to the reconnection time of
|
|
the event source, if the <code title="dom-EventSource-readyState"><a href="#dom-eventsource-readystate">readyState</a></code> attribute is
|
|
still set to <code title="dom-EventSource-CONNECTING"><a href="#dom-eventsource-connecting">CONNECTING</a></code>, once again do
|
|
a <span>potentially CORS-enabled fetch</span> of the <span>absolute
|
|
URL</span> of the event source resource, with the <i>mode</i> being
|
|
<span title="attr-crossorigin-use-credentials">Use
|
|
Credentials</span>, and the <i title="">origin</i> being the same as the
|
|
<span>origin</span> used in the original request triggered by the
|
|
<code title="dom-EventSource"><a href="#dom-eventsource">EventSource()</a></code> constructor, and process the
|
|
resource obtained in this fashion, if any, as described in this
|
|
section.<p>When a user agent is to <dfn id="fail-the-connection">fail the connection</dfn>, the user
|
|
agent must <span>queue a task</span> to set the <code title="dom-EventSource-readyState"><a href="#dom-eventsource-readystate">readyState</a></code> attribute to
|
|
<code title="dom-EventSource-CLOSED"><a href="#dom-eventsource-closed">CLOSED</a></code> and <span>fire a
|
|
simple event</span> named <code title="event-error">error</code> at
|
|
the <code><a href="#eventsource">EventSource</a></code> object. <strong>Once the user agent has
|
|
<a href="#fail-the-connection" title="fail the connection">failed the connection</a>, it
|
|
does <em>not</em> attempt to reconnect!</strong><hr><p>The <span>task source</span> for any <span title="concept-task">tasks</span> that are <span title="queue a
|
|
task">queued</span> by <code><a href="#eventsource">EventSource</a></code> objects is the
|
|
<dfn id="remote-event-task-source">remote event task source</dfn>.<h2 id="parsing-an-event-stream"><span class="secno">6 </span>Parsing an event stream</h2><p>This event stream format's <span>MIME type</span> is
|
|
<code><a href="#text-event-stream">text/event-stream</a></code>.<p>The event stream format is as described by the <code title="">stream</code> production of the following ABNF, the
|
|
character set for which is Unicode. <a href="#refsABNF">[ABNF]</a><pre>stream = [ bom ] *event
|
|
event = *( comment / field ) end-of-line
|
|
comment = colon *any-char end-of-line
|
|
field = 1*name-char [ colon [ space ] *any-char ] end-of-line
|
|
end-of-line = ( cr lf / cr / lf )
|
|
|
|
; characters
|
|
lf = %x000A ; U+000A LINE FEED (LF)
|
|
cr = %x000D ; U+000D CARRIAGE RETURN (CR)
|
|
space = %x0020 ; U+0020 SPACE
|
|
colon = %x003A ; U+003A COLON (:)
|
|
bom = %xFEFF ; U+FEFF BYTE ORDER MARK
|
|
name-char = %x0000-0009 / %x000B-000C / %x000E-0039 / %x003B-10FFFF
|
|
; a <span>Unicode character</span> other than U+000A LINE FEED (LF), U+000D CARRIAGE RETURN (CR), or U+003A COLON (:)
|
|
any-char = %x0000-0009 / %x000B-000C / %x000E-10FFFF
|
|
; a <span>Unicode character</span> other than U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR)</pre><p>Event streams in this format must always be encoded as
|
|
UTF-8. <a href="#refsRFC3629">[RFC3629]</a><p>Lines must be separated by either a U+000D CARRIAGE RETURN U+000A
|
|
LINE FEED (CRLF) character pair, a single U+000A LINE FEED (LF)
|
|
character, or a single U+000D CARRIAGE RETURN (CR) character.<p>Since connections established to remote servers for such
|
|
resources are expected to be long-lived, UAs should ensure that
|
|
appropriate buffering is used. In particular, while line buffering
|
|
with lines are defined to end with a single U+000A LINE FEED (LF)
|
|
character is safe, block buffering or line buffering with different
|
|
expected line endings can cause delays in event dispatch.<h2 id="event-stream-interpretation"><span class="secno">7 </span>Interpreting an event stream</h2><p>Streams must be <span>decoded as UTF-8, with error
|
|
handling</span>.
|
|
|
|
<a href="#refsHTML">[HTML]</a>
|
|
|
|
<p>One leading U+FEFF BYTE ORDER MARK character must be ignored if
|
|
any are present.<p>The stream must then be parsed by reading everything line by
|
|
line, with a U+000D CARRIAGE RETURN U+000A LINE FEED (CRLF)
|
|
character pair, a single U+000A LINE FEED (LF) character not
|
|
preceded by a U+000D CARRIAGE RETURN (CR) character, a single U+000D
|
|
CARRIAGE RETURN (CR) character not followed by a U+000A LINE FEED
|
|
(LF) character, and the end of the file being the four ways in which
|
|
a line can end.<p>When a stream is parsed, a <var title="">data</var> buffer, an
|
|
<var title="">event name</var> buffer, and a <var title="">last
|
|
event ID</var> buffer must be associated with it. They must be
|
|
initialized to the empty string<p>Lines must be processed, in the order they are received, as
|
|
follows:<dl class="switch"><dt>If the line is empty (a blank line)</dt>
|
|
|
|
<dd><p><a href="#dispatchMessage">Dispatch the event</a>, as
|
|
defined below.</dd>
|
|
|
|
|
|
<dt>If the line starts with a U+003A COLON character (:)</dt>
|
|
|
|
<dd><p>Ignore the line.</dd>
|
|
|
|
|
|
<dt>If the line contains a U+003A COLON character (:)</dt>
|
|
|
|
<dd>
|
|
|
|
<p>Collect the characters on the line before the first U+003A
|
|
COLON character (:), and let <var title="">field</var> be that
|
|
string.</p>
|
|
|
|
<p>Collect the characters on the line after the first U+003A COLON
|
|
character (:), and let <var title="">value</var> be that
|
|
string. If <var title="">value</var> starts with a U+0020
|
|
SPACE character, remove it from <var title="">value</var>.</p>
|
|
|
|
<p><a href="#processField">Process the field</a> using the steps
|
|
described below, using <var title="">field</var> as the field name
|
|
and <var title="">value</var> as the field value.</p>
|
|
|
|
</dd>
|
|
|
|
|
|
<dt>Otherwise, the string is not empty but does not contain a U+003A COLON character (:)</dt>
|
|
|
|
<dd>
|
|
|
|
<p><a href="#processField">Process the field</a> using the steps
|
|
described below, using the whole line as the field name, and
|
|
the empty string as the field value.</p>
|
|
|
|
</dd>
|
|
|
|
</dl><p>Once the end of the file is reached, any pending data must be
|
|
discarded. (If the file ends in the middle of an event, before the
|
|
final empty line, the incomplete event is not dispatched.)<hr><p id="processField">The steps to <dfn title="">process the
|
|
field</dfn> given a field name and a field value depend on the field
|
|
name, as given in the following list. Field names must be compared
|
|
literally, with no case folding performed.<dl class="switch"><dt>If the field name is "event"</dt>
|
|
|
|
<dd><p>Set the <var title="">event name</var> buffer to field
|
|
value.</dd>
|
|
|
|
|
|
<dt>If the field name is "data"</dt>
|
|
|
|
<dd><p>Append the field value to the <var title="">data</var>
|
|
buffer, then append a single U+000A LINE FEED (LF) character to the
|
|
<var title="">data</var> buffer.</dd>
|
|
|
|
|
|
<dt>If the field name is "id"</dt>
|
|
|
|
<dd><p>Set the <var title="">last event ID</var> buffer to the
|
|
field value.</dd>
|
|
|
|
|
|
<dt>If the field name is "retry"</dt>
|
|
|
|
<dd><p>If the field value consists of only characters in the range
|
|
U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), then interpret the
|
|
field value as an integer in base ten, and set the event stream's
|
|
<a href="#concept-event-stream-reconnection-time" title="concept-event-stream-reconnection-time">reconnection
|
|
time</a> to that integer. Otherwise, ignore the field.</dd>
|
|
|
|
|
|
|
|
<dt>Otherwise</dt>
|
|
|
|
<dd><p>The field is ignored.</dd>
|
|
|
|
</dl><p id="dispatchMessage">When the user agent is required to <dfn title="">dispatch the event</dfn>, then the user agent must act as
|
|
follows:
|
|
|
|
<ol><li><p>Set the <a href="#concept-event-stream-last-event-id" title="concept-event-stream-last-event-id">last event ID
|
|
string</a> of the event source to value of the <var title="">last event ID</var> buffer. The buffer does not get reset,
|
|
so the <a href="#concept-event-stream-last-event-id" title="concept-event-stream-last-event-id">last event
|
|
ID string</a> of the event source remains set to this value
|
|
until the next time it is set by the server.</li>
|
|
|
|
<li><p>If the <var title="">data</var> buffer is an empty string,
|
|
set the <var title="">data</var> buffer and the <var title="">event
|
|
name</var> buffer to the empty string and abort these
|
|
steps.</li>
|
|
|
|
<li><p>If the <var title="">data</var> buffer's last character is a
|
|
U+000A LINE FEED (LF) character, then remove the last character
|
|
from the <var title="">data</var> buffer.</li>
|
|
|
|
<li><p>Create an event that uses the <code>MessageEvent</code>
|
|
interface, with the event name <code title="event-message">message</code>, which does not bubble, is not
|
|
cancelable, and has no default action. The <code title="dom-MessageEvent-data">data</code> attribute must be
|
|
initialized to the value of the <var title="">data</var> buffer,
|
|
the <code title="dom-MessageEvent-origin">origin</code> attribute
|
|
must be initialized to the <span title="Unicode serialization of an
|
|
origin">Unicode serialization</span> of the <span>origin</span> of
|
|
the event stream's URL, and the <code title="dom-MessageEvent-lastEventId">lastEventId</code> attribute
|
|
must be initialized to the <a href="#concept-event-stream-last-event-id" title="concept-event-stream-last-event-id">last event ID
|
|
string</a> of the event source.</li>
|
|
|
|
<li><p>If the <var title="">event name</var> buffer has a value
|
|
other than the empty string, change the <span title="concept-event-type">type</span> of the newly created event
|
|
to equal the value of the <var title="">event name</var>
|
|
buffer.</li>
|
|
|
|
<li><p>Set the <var title="">data</var> buffer and the <var title="">event name</var> buffer to the empty string.</li>
|
|
|
|
<li><p><span>Queue a task</span> which, if the <code title="dom-EventSource-readyState"><a href="#dom-eventsource-readystate">readyState</a></code> attribute is
|
|
set to a value other than <code title="dom-EventSource-CLOSED"><a href="#dom-eventsource-closed">CLOSED</a></code>, dispatches the newly
|
|
created event at the <code><a href="#eventsource">EventSource</a></code> object.</li>
|
|
</ol><p class="note">If an event doesn't have an "id" field, but an
|
|
earlier event did set the event source's <a href="#concept-event-stream-last-event-id" title="concept-event-stream-last-event-id">last event ID
|
|
string</a>, then the event's <code title="dom-MessageEvent-lastEventId">lastEventId</code> field will
|
|
be set to the value of whatever the last seen "id" field was.<div class="example">
|
|
|
|
<p>The following event stream, once followed by a blank line:</p>
|
|
<pre>data: YHOO
|
|
data: +2
|
|
data: 10</pre>
|
|
|
|
<p>...would cause an event <code title="event-message">message</code> with the interface
|
|
<code>MessageEvent</code> to be dispatched on the
|
|
<code><a href="#eventsource">EventSource</a></code> object. The event's <code title="dom-MessageEvent-data">data</code> attribute would contain
|
|
the string <code>YHOO\n+2\n10</code> (where <code>\n</code>
|
|
represents a newline).</p>
|
|
|
|
<p>This could be used as follows:
|
|
<pre>var stocks = new EventSource("http://stocks.example.com/ticker.php");
|
|
stocks.onmessage = function (event) {
|
|
var data = event.data.split('\n');
|
|
updateStocks(data[0], data[1], data[2]);
|
|
};</pre>
|
|
|
|
<p>...where <code title="">updateStocks()</code> is a function defined as:</p>
|
|
|
|
<pre>function updateStocks(symbol, delta, value) { ... }</pre>
|
|
|
|
<p>...or some such.</p>
|
|
|
|
</div><div class="example">
|
|
|
|
<p>The following stream contains four blocks. The first block has
|
|
just a comment, and will fire nothing. The second block has two
|
|
fields with names "data" and "id" respectively; an event will be
|
|
fired for this block, with the data "first event", and will then
|
|
set the last event ID to "1" so that if the connection died between
|
|
this block and the next, the server would be sent a <code title="http-last-event-id"><a href="#last-event-id">Last-Event-ID</a></code> header with the
|
|
value "1". The third block fires an event with data "second event",
|
|
and also has an "id" field, this time with no value, which resets
|
|
the last event ID to the empty string (meaning no <code title="http-last-event-id"><a href="#last-event-id">Last-Event-ID</a></code> header will now be
|
|
sent in the event of a reconnection being attempted). Finally, the
|
|
last block just fires an event with the data
|
|
" third event" (with a single leading space character).
|
|
Note that the last still has to end with a blank line, the end of
|
|
the stream is not enough to trigger the dispatch of the last
|
|
event.</p>
|
|
|
|
<pre>: test stream
|
|
|
|
data: first event
|
|
id: 1
|
|
|
|
data:second event
|
|
id
|
|
|
|
data: third event
|
|
</pre>
|
|
</div><div class="example">
|
|
|
|
<p>The following stream fires two events:</p>
|
|
|
|
<pre>data
|
|
|
|
data
|
|
data
|
|
|
|
data:</pre>
|
|
|
|
<p>The first block fires events with the data set to the empty
|
|
string, as would the last block if it was followed by a blank line.
|
|
The middle block fires an event with the data set to a single
|
|
newline character. The last block is discarded because it is not
|
|
followed by a blank line.</p>
|
|
|
|
</div><div class="example">
|
|
|
|
<p>The following stream fires two identical events:</p>
|
|
|
|
<pre>data:test
|
|
|
|
data: test
|
|
</pre>
|
|
|
|
<p>This is because the space after the colon is ignored if
|
|
present.</p>
|
|
|
|
</div><h2 id="notes"><span class="secno">8 </span>Notes</h2><p>Legacy proxy servers are known to, in certain cases, drop HTTP
|
|
connections after a short timeout. To protect against such proxy
|
|
servers, authors can include a comment line (one starting with a ':'
|
|
character) every 15 seconds or so.<p>Authors wishing to relate event source connections to each other
|
|
or to specific documents previously served might find that relying
|
|
on IP addresses doesn't work, as individual clients can have
|
|
multiple IP addresses (due to having multiple proxy servers) and
|
|
individual IP addresses can have multiple clients (due to sharing a
|
|
proxy server). It is better to include a unique identifier in the
|
|
document when it is served and then pass that identifier as part of
|
|
the URL when the connection is established.<p>Authors are also cautioned that HTTP chunking can have unexpected
|
|
negative effects on the reliability of this protocol. Where
|
|
possible, chunking should be disabled for serving event streams
|
|
unless the rate of messages is high enough for this not to
|
|
matter.</p><p>Clients that support HTTP's per-server connection limitation
|
|
might run into trouble when opening multiple pages from a site if
|
|
each page has an <code><a href="#eventsource">EventSource</a></code> to the same
|
|
domain. Authors can avoid this using the relatively complex
|
|
mechanism of using unique domain names per connection, or by
|
|
allowing the user to enable or disable the <code><a href="#eventsource">EventSource</a></code>
|
|
functionality on a per-page basis, or by sharing a single
|
|
<code><a href="#eventsource">EventSource</a></code> object using a <span title="SharedWorkerGlobalScope">shared worker</span>.
|
|
|
|
<a href="#refsWEBWORKERS">[WEBWORKERS]</a>
|
|
|
|
<h2 id="eventsource-push"><span class="secno">9 </span>Connectionless push and other features</h2><p>User agents running in controlled environments, e.g. browsers on
|
|
mobile handsets tied to specific carriers, may offload the
|
|
management of the connection to a proxy on the network. In such a
|
|
situation, the user agent for the purposes of conformance is
|
|
considered to include both the handset software and the network
|
|
proxy.<div class="example">
|
|
|
|
<p>For example, a browser on a mobile device, after having
|
|
established a connection, might detect that it is on a supporting
|
|
network and request that a proxy server on the network take over
|
|
the management of the connection. The timeline for such a situation
|
|
might be as follows:</p>
|
|
|
|
<ol><li>Browser connects to a remote HTTP server and requests the
|
|
resource specified by the author in the <code title="dom-EventSource"><a href="#dom-eventsource">EventSource</a></code> constructor.</li>
|
|
|
|
<li>The server sends occasional messages.</li>
|
|
|
|
<li>In between two messages, the browser detects that it is idle
|
|
except for the network activity involved in keeping the TCP
|
|
connection alive, and decides to switch to sleep mode to save power.</li>
|
|
|
|
<li>The browser disconnects from the server.</li>
|
|
|
|
<li>The browser contacts a service on the network, and requests
|
|
that that service, a "push proxy", maintain the connection instead.</li>
|
|
|
|
<li>The "push proxy" service contacts the remote HTTP server and
|
|
requests the resource specified by the author in the <code title="dom-EventSource"><a href="#dom-eventsource">EventSource</a></code> constructor (possibly
|
|
including a <code title="http-last-event-id"><a href="#last-event-id">Last-Event-ID</a></code>
|
|
HTTP header, etc).</li>
|
|
|
|
<li>The browser allows the mobile device to go to sleep.</li>
|
|
|
|
<li>The server sends another message.</li>
|
|
|
|
<li>The "push proxy" service uses a technology such as OMA push to
|
|
convey the event to the mobile device, which wakes only
|
|
enough to process the event and then returns to sleep.</li>
|
|
|
|
</ol></div><p>This can reduce the total data usage, and can therefore result in
|
|
considerable power savings.<p>As well as implementing the existing API and
|
|
<code><a href="#text-event-stream">text/event-stream</a></code> wire format as defined by this
|
|
specification and in more distributed ways as described above,
|
|
formats of event framing defined by <span>other applicable
|
|
specifications</span> may be supported. This specification does not
|
|
define how they are to be parsed or processed.<h2 id="garbage-collection"><span class="secno">10 </span>Garbage collection</h2><p>While an <code><a href="#eventsource">EventSource</a></code> object's <code title="dom-EventSource-readyState"><a href="#dom-eventsource-readystate">readyState</a></code> is <code title="dom-EventSource-CONNECTING"><a href="#dom-eventsource-connecting">CONNECTING</a></code>, and the object
|
|
has one or more event listeners registered for <code title="event-open">open</code>, <code title="event-message">message</code> or <code title="event-error">error</code> events, there must be a strong
|
|
reference from the <code>Window</code> or <code>WorkerUtils</code>
|
|
object that the <code><a href="#eventsource">EventSource</a></code> object's constructor was
|
|
invoked from to the <code><a href="#eventsource">EventSource</a></code> object itself.<p>While an <code><a href="#eventsource">EventSource</a></code> object's <code title="dom-EventSource-readyState"><a href="#dom-eventsource-readystate">readyState</a></code> is <code title="dom-EventSource-OPEN"><a href="#dom-eventsource-open">OPEN</a></code>, and the object has one or
|
|
more event listeners registered for <code title="event-message">message</code> or <code title="event-error">error</code> events, there must be a strong
|
|
reference from the <code>Window</code> or <code>WorkerUtils</code>
|
|
object that the <code><a href="#eventsource">EventSource</a></code> object's constructor was
|
|
invoked from to the <code><a href="#eventsource">EventSource</a></code> object itself.<p>While there is a task queued by an <code><a href="#eventsource">EventSource</a></code>
|
|
object on the <a href="#remote-event-task-source">remote event task source</a>, there must be a
|
|
strong reference from the <code>Window</code> or
|
|
<code>WorkerUtils</code> object that the <code><a href="#eventsource">EventSource</a></code>
|
|
object's constructor was invoked from to that
|
|
<code><a href="#eventsource">EventSource</a></code> object.<p>If a user agent is to <dfn id="concept-eventsource-forcibly-close" title="concept-EventSource-forcibly-close">forcibly close</dfn> an
|
|
<code><a href="#eventsource">EventSource</a></code> object (this happens when a
|
|
<code>Document</code> object goes away permanently), the user agent
|
|
must abort any instances of the <span>fetch</span> algorithm started
|
|
for this <code><a href="#eventsource">EventSource</a></code> object, and must set the <code title="dom-EventSource-readyState"><a href="#dom-eventsource-readystate">readyState</a></code> attribute to
|
|
<code title="dom-EventSource-CLOSED"><a href="#dom-eventsource-closed">CLOSED</a></code>.</p><p>If an <code><a href="#eventsource">EventSource</a></code> object is garbage collected while
|
|
its connection is still open, the user agent must abort any instance
|
|
of the <span title="fetch">fetch</span> algorithm opened by this
|
|
<code><a href="#eventsource">EventSource</a></code>.</p><p class="note">It's possible for one active network connection to
|
|
be shared by multiple <code><a href="#eventsource">EventSource</a></code> objects and their
|
|
<span>fetch</span> algorithms, which is why the above is phrased in
|
|
terms of aborting the <span>fetch</span> algorithm and not the
|
|
actual underlying download.<h2 id="iana-considerations"><span class="secno">11 </span>IANA considerations</h2><h3 id="text-event-stream"><span class="secno">11.1 </span><dfn><code>text/event-stream</code></dfn></h3><p>This registration is for community review and will be submitted
|
|
to the IESG for review, approval, and registration with IANA.</p><dl><dt>Type name:</dt>
|
|
<dd>text</dd>
|
|
<dt>Subtype name:</dt>
|
|
<dd>event-stream</dd>
|
|
<dt>Required parameters:</dt>
|
|
<dd>No parameters</dd>
|
|
<dt>Optional parameters:</dt>
|
|
<dd>
|
|
<dl><dt><code title="">charset</code></dt>
|
|
<dd>
|
|
|
|
<p>The <code title="">charset</code> parameter may be provided.
|
|
The parameter's value must be "<code title="">utf-8</code>".
|
|
This parameter serves no purpose; it is only allowed for
|
|
compatibility with legacy servers.</p>
|
|
|
|
</dd>
|
|
</dl></dd>
|
|
<dt>Encoding considerations:</dt>
|
|
<dd>8bit (always UTF-8)</dd>
|
|
<dt>Security considerations:</dt>
|
|
<dd>
|
|
|
|
<p>An event stream from an origin distinct from the origin of the
|
|
content consuming the event stream can result in information
|
|
leakage. To avoid this, user agents are required to apply CORS
|
|
semantics. <a href="#refsCORS">[CORS]</a></p>
|
|
|
|
<p>Event streams can overwhelm a user agent; a user agent is
|
|
expected to apply suitable restrictions to avoid depleting local
|
|
resources because of an overabundance of information from an event
|
|
stream.</p>
|
|
|
|
<p>Servers can be overwhelmed if a situation develops in which the
|
|
server is causing clients to reconnect rapidly. Servers should use
|
|
a 5xx status code to indicate capacity problems, as this will
|
|
prevent conforming clients from reconnecting automatically.</p>
|
|
|
|
</dd>
|
|
<dt>Interoperability considerations:</dt>
|
|
<dd>
|
|
Rules for processing both conforming and non-conforming content
|
|
are defined in this specification.
|
|
</dd>
|
|
<dt>Published specification:</dt>
|
|
<dd>
|
|
This document is the relevant specification.
|
|
</dd>
|
|
<dt>Applications that use this media type:</dt>
|
|
<dd>
|
|
Web browsers and tools using Web services.
|
|
</dd>
|
|
<dt>Additional information:</dt>
|
|
<dd>
|
|
<dl><dt>Magic number(s):</dt>
|
|
<dd>No sequence of bytes can uniquely identify an event stream.</dd>
|
|
<dt>File extension(s):</dt>
|
|
<dd>No specific file extensions are recommended for this type.</dd>
|
|
<dt>Macintosh file type code(s):</dt>
|
|
<dd>No specific Macintosh file type codes are recommended for this type.</dd>
|
|
</dl></dd>
|
|
<dt>Person & email address to contact for further information:</dt>
|
|
<dd>Ian Hickson <ian@hixie.ch></dd>
|
|
<dt>Intended usage:</dt>
|
|
<dd>Common</dd>
|
|
<dt>Restrictions on usage:</dt>
|
|
<dd>This format is only expected to be used by dynamic open-ended
|
|
streams served using HTTP or a similar protocol. Finite resources
|
|
are not expected to be labeled with this type.</dd>
|
|
<dt>Author:</dt>
|
|
<dd>Ian Hickson <ian@hixie.ch></dd>
|
|
<dt>Change controller:</dt>
|
|
<dd>W3C</dd>
|
|
</dl><p>Fragment identifiers have no meaning with
|
|
<code><a href="#text-event-stream">text/event-stream</a></code> resources.<h3 id="last-event-id"><span class="secno">11.2 </span><dfn title="http-last-event-id"><code>Last-Event-ID</code></dfn></h3><p>This section describes a header field for registration in the
|
|
Permanent Message Header Field Registry. <a href="#refsRFC3864">[RFC3864]</a><dl><dt>Header field name</dt>
|
|
<dd>Last-Event-ID</dd>
|
|
<dt>Applicable protocol</dt>
|
|
<dd>http</dd>
|
|
<dt>Status</dt>
|
|
<dd>standard</dd>
|
|
<dt>Author/Change controller</dt>
|
|
<dd>W3C</dd>
|
|
<dt>Specification document(s)</dt>
|
|
<dd>
|
|
This document is the relevant specification.
|
|
</dd>
|
|
<dt>Related information</dt>
|
|
<dd>None.</dd>
|
|
</dl><h2 class="no-num" id="references">References</h2><p>All references are normative unless marked "Non-normative".</p><dl><dt id="refsABNF">[ABNF]</dt>
|
|
<dd><cite><a href="http://www.ietf.org/rfc/std/std68.txt">Augmented
|
|
BNF for Syntax Specifications: ABNF</a></cite>, D. Crocker,
|
|
P. Overell. IETF.</dd>
|
|
|
|
<dt id="refsCORS">[CORS]</dt>
|
|
<dd><cite><a href="http://dev.w3.org/2006/waf/access-control/">Cross-Origin
|
|
Resource Sharing</a></cite>, A. van Kesteren. W3C.</dd>
|
|
|
|
<dt id="refsDOMCORE">[DOMCORE]</dt>
|
|
<dd><cite><a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html">Web DOM Core</a></cite>, A. van Kesteren. W3C.</dd>
|
|
|
|
<dt id="refsHTML">[HTML]</dt>
|
|
<dd><cite><a href="http://www.w3.org/TR/html5/">HTML5</a></cite>,
|
|
I. Hickson. W3C.</dd>
|
|
|
|
<dt id="refsRFC2119">[RFC2119]</dt>
|
|
<dd><cite><a href="http://tools.ietf.org/html/rfc2119">Key words for use in
|
|
RFCs to Indicate Requirement Levels</a></cite>, S. Bradner. IETF.</dd>
|
|
|
|
<dt id="refsRFC3629">[RFC3629]</dt>
|
|
<dd><cite><a href="http://tools.ietf.org/html/rfc3629">UTF-8, a
|
|
transformation format of ISO 10646</a></cite>, F. Yergeau. IETF.</dd>
|
|
|
|
<dt id="refsRFC3864">[RFC3864]</dt>
|
|
<dd><cite><a href="http://tools.ietf.org/html/rfc3864">Registration Procedures
|
|
for Message Header Fields</a></cite>, G. Klyne, M. Nottingham,
|
|
J. Mogul. IETF.</dd>
|
|
|
|
<dt id="refsWEBIDL">[WEBIDL]</dt>
|
|
<dd><cite><a href="http://dev.w3.org/2006/webapi/WebIDL/">Web
|
|
IDL</a></cite>, C. McCormack. W3C.</dd>
|
|
|
|
<dt id="refsWEBWORKERS">[WEBWORKERS]</dt>
|
|
<dd><cite><a href="http://dev.w3.org/html5/workers/">Web
|
|
Workers</a></cite>, I. Hickson. W3C.</dd>
|
|
|
|
</dl><h2 class="no-num" id="acknowledgements">Acknowledgements</h2><p>For a full list of acknowledgements, please see the HTML
|
|
specification. <a href="#refsHTML">[HTML]</a>
|
|
</body>
|
|
</html>
|