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   <title>Chapter&nbsp;26.&nbsp;WebSocket Introduction</title><link rel="stylesheet" type="text/css" href="css/docbook.css"><meta name="generator" content="DocBook XSL Stylesheets V1.79.1"><meta name="keywords" content="jetty, servlet, servlet-api, cometd, http, websocket, eclipse, maven, java, server, software"><link rel="home" href="index.html" title="Jetty"><link rel="up" href="jetty-dev-guide.html" title="Part&nbsp;IV.&nbsp;Jetty Development Guide"><link rel="prev" href="jetty-handlers.html" title="Chapter&nbsp;25.&nbsp;Handlers"><link rel="next" href="ws-intro-api.html" title="WebSocket APIs"><link xmlns:jfetch="java:org.eclipse.jetty.xslt.tools.JavaSourceFetchExtension" xmlns:fetch="java:org.eclipse.jetty.xslt.tools.SourceFetchExtension" xmlns:d="http://docbook.org/ns/docbook" xmlns:l="http://docbook.sourceforge.net/xmlns/l10n/1.0" xmlns:xslthl="http://xslthl.sf.net" xmlns:gcse="http://www.google.com" xmlns:date="http://exslt.org/dates-and-times" rel="shortcut icon" href="images/favicon.ico"><link rel="stylesheet" href="css/highlighter/foundation.css"><script src="js/highlight.pack.js"></script><script>
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      </p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="websocket-intro"></a>Chapter&nbsp;26.&nbsp;WebSocket Introduction</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="websocket-intro.html#ws-intro-provides">What Jetty provides</a></span></dt><dt><span class="section"><a href="ws-intro-api.html">WebSocket APIs</a></span></dt><dt><span class="section"><a href="_enabling_websocket.html">Enabling WebSocket</a></span></dt></dl></div><p>WebSocket is a new protocol for bidirectional communications over HTTP.</p><p>It is based on a low level framing protocol that delivers messages in either UTF-8 TEXT or BINARY format.</p><p>A single message in WebSocket can be of any size (the underlying framing however does have a single frame limit of <a class="link" href="http://en.wikipedia.org/wiki/9223372036854775807" target="_top">63-bits</a>)</p><p>There can be an unlimited number of messages sent.</p><p>Messages are sent sequentially, the base protocol does not support interleaved messages.</p><p>A WebSocket connection goes through some basic state changes:</p><div class="table"><a name="d0e22875"></a><p class="title"><b>Table&nbsp;26.1.&nbsp;WebSocket connection states</b></p><div class="table-contents"><table class="table" summary="WebSocket connection states" border="1" width="50%"><colgroup><col class="col_1"><col class="col_2"></colgroup><thead><tr><th align="left" valign="top">State</th><th align="left" valign="top">Description</th></tr></thead><tbody><tr><td align="left" valign="top"><p>CONNECTING</p></td><td align="left" valign="top"><p>A HTTP Upgrade to WebSocket is in progress</p></td></tr><tr><td align="left" valign="top"><p>OPEN</p></td><td align="left" valign="top"><p>The HTTP Upgrade succeeded and the socket is now open and ready to read / write</p></td></tr><tr><td align="left" valign="top"><p>CLOSING</p></td><td align="left" valign="top"><p>A WebSocket Close Handshake has been started</p></td></tr><tr><td align="left" valign="top"><p>CLOSED</p></td><td align="left" valign="top"><p>WebSocket is now closed, no more read/write possible</p></td></tr></tbody></table></div></div><br class="table-break"><p>When a WebSocket is closed, a <a class="link" href="http://www.eclipse.org/jetty/javadoc/9.3.28.v20191105/org/eclipse/jetty/websocket/api/StatusCode.html" target="_top">status code</a> and short reason string is provided.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="ws-intro-provides"></a>What Jetty provides</h2></div></div></div><p>Jetty provides an implementation of the following standards and specs.</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><a class="link" href="http://tools.ietf.org/html/rfc6455" target="_top">RFC-6455</a></span></dt><dd><p class="simpara">The WebSocket Protocol</p><p class="simpara">We support the version 13 of the released and final spec.</p><p class="simpara">Jetty tests its WebSocket protocol implementation using the <a class="link" href="http://autobahn.ws/testsuite" target="_top">autobahn testsuite</a>.</p></dd></dl></div><div class="blockquote"><blockquote class="blockquote"><div xmlns:jfetch="java:org.eclipse.jetty.xslt.tools.JavaSourceFetchExtension" xmlns:fetch="java:org.eclipse.jetty.xslt.tools.SourceFetchExtension" xmlns:d="http://docbook.org/ns/docbook" xmlns:l="http://docbook.sourceforge.net/xmlns/l10n/1.0" xmlns:xslthl="http://xslthl.sf.net" xmlns:gcse="http://www.google.com" xmlns:date="http://exslt.org/dates-and-times" class="important" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title"><i class="fa fa-plus" aria-hidden="true"></i> Important</h3><p>The early drafts of WebSocket were supported in Jetty 7 and Jetty 8,   but this support has been removed in Jetty 9.
This means that Jetty 9 will not support the old browsers that implemented the early drafts of WebSocket. (such as Safari 5.0 or Opera 12)</p></div></blockquote></div><div class="blockquote"><blockquote class="blockquote"><div xmlns:jfetch="java:org.eclipse.jetty.xslt.tools.JavaSourceFetchExtension" xmlns:fetch="java:org.eclipse.jetty.xslt.tools.SourceFetchExtension" xmlns:d="http://docbook.org/ns/docbook" xmlns:l="http://docbook.sourceforge.net/xmlns/l10n/1.0" xmlns:xslthl="http://xslthl.sf.net" xmlns:gcse="http://www.google.com" xmlns:date="http://exslt.org/dates-and-times" class="tip" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title"><i class="fa fa-lightbulb-o" aria-hidden="true"></i> Tip</h3><p>Want to know if the browser you are targeting supports WebSocket?
Use <a class="link" href="http://caniuse.com/websockets" target="_top">caniuse.com/websockets</a> to find out.</p></div></blockquote></div><div class="variablelist"><dl class="variablelist"><dt><span class="term"><a class="link" href="http://www.jcp.org/en/jsr/detail?id=356" target="_top">JSR-356</a></span></dt><dd><p class="simpara">The Java WebSocket API (<code class="literal">javax.websocket</code>)</p><p class="simpara">This is the official Java API for working with WebSockets.</p></dd></dl></div><p>Unstable standards and specs:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><a class="link" href="https://datatracker.ietf.org/doc/draft-ietf-hybi-websocket-perframe-compression/" target="_top">perframe-compression</a></span></dt><dd><p class="simpara">Per Frame Compression Extension.</p><p class="simpara">An early extension draft from the Google/Chromium team that would provide WebSocket frame compression.</p><p class="simpara">perframe-compression using deflate algorithm is present on many versions of Chrome/Chromium.</p><p class="simpara">Jetty&#8217;s support for perframe-compression is based on the draft-04 spec.</p><p class="simpara">This standard is being replaced with permessage-compression.</p></dd><dt><span class="term"><a class="link" href="https://datatracker.ietf.org/doc/draft-tyoshino-hybi-permessage-compression/" target="_top">permessage-compression</a></span></dt><dd><p class="simpara">Per Frame Compression Extension.</p><p class="simpara">This is the replacement for perframe-compression, switching the compression to being based on the entire message, not the individual frames.</p></dd></dl></div></div></div><script type="text/javascript">
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