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<h1 class="lined-header"><span>cowboy_websocket(3)</span></h1>
<div class="sect1">
<h2 id="_name">Name</h2>
<div class="sectionbody">
<div class="paragraph"><p>cowboy_websocket - Websocket protocol</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_description">Description</h2>
<div class="sectionbody">
<div class="paragraph"><p>The <code>cowboy_websocket</code> module implements the Websocket protocol.</p></div>
<div class="paragraph"><p>This module is a sub protocol that defines four callbacks to
be implemented by handlers. The <code>init/2</code> and <code>terminate/3</code>
callbacks are common to all handler types and are documented
in the manual for the <a href="cowboy_handler.asciidoc">cowboy_handler</a> module.</p></div>
<div class="paragraph"><p>The <code>websocket_handle/2</code> and <code>websocket_info/2</code> callbacks are
specific to Websocket handlers and will be called as many times
as necessary until the Websocket connection is closed.</p></div>
<div class="paragraph"><p>The <code>init/2</code> callback can be used to negotiate Websocket protocol
extensions with the client. It is highly recommended to return a
timeout value from this callback to ensure that the process is
terminated when no data has been received during that timespan.
The default timeout is <code>infinity</code>, which should only be used if
you have alternate means of ending inactive connections.</p></div>
<div class="paragraph"><p>Cowboy will terminate the process right after closing the
Websocket connection. This means that there is no real need to
perform any cleanup in the optional <code>terminate/3</code> callback.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_meta_values">Meta values</h2>
<div class="sectionbody">
<div class="dlist"><dl>
<dt class="hdlist1">
websocket_compress = boolean()
</dt>
<dd>
<p>
Whether a websocket compression extension in in use.
</p>
</dd>
<dt class="hdlist1">
websocket_version = 7 | 8 | 13
</dt>
<dd>
<p>
The version of the Websocket protocol being used.
</p>
</dd>
</dl></div>
</div>
</div>
<div class="sect1">
<h2 id="_terminate_reasons">Terminate reasons</h2>
<div class="sectionbody">
<div class="paragraph"><p>The following values may be received as the terminate reason
in the optional <code>terminate/3</code> callback.</p></div>
<div class="dlist"><dl>
<dt class="hdlist1">
normal
</dt>
<dd>
<p>
The connection was closed normally before establishing a Websocket
connection. This typically happens if an <code>ok</code> tuple is returned
from the <code>init/2</code> callback.
</p>
</dd>
<dt class="hdlist1">
remote
</dt>
<dd>
<p>
The remote endpoint closed the connection without giving any
further details.
</p>
</dd>
<dt class="hdlist1">
{remote, Code, Payload}
</dt>
<dd>
<p>
The remote endpoint closed the connection with the given
<code>Code</code> and <code>Payload</code> as the reason.
</p>
</dd>
<dt class="hdlist1">
stop
</dt>
<dd>
<p>
The handler requested to close the connection, either by returning
a <code>stop</code> tuple or by sending a <code>close</code> frame.
</p>
</dd>
<dt class="hdlist1">
timeout
</dt>
<dd>
<p>
The connection has been closed due to inactivity. The timeout
value can be configured from <code>init/2</code>.
</p>
</dd>
<dt class="hdlist1">
{crash, Class, Reason}
</dt>
<dd>
<p>
A crash occurred in the handler. <code>Class</code> and <code>Reason</code> can be
used to obtain more information about the crash. The function
<code>erlang:get_stacktrace/0</code> can also be called to obtain the
stacktrace of the process when the crash occurred.
</p>
</dd>
<dt class="hdlist1">
{error, badencoding}
</dt>
<dd>
<p>
A text frame was sent by the client with invalid encoding. All
text frames must be valid UTF-8.
</p>
</dd>
<dt class="hdlist1">
{error, badframe}
</dt>
<dd>
<p>
A protocol error has been detected.
</p>
</dd>
<dt class="hdlist1">
{error, closed}
</dt>
<dd>
<p>
The socket has been closed brutally without a close frame being
received first.
</p>
</dd>
<dt class="hdlist1">
{error, Reason}
</dt>
<dd>
<p>
A socket error ocurred.
</p>
</dd>
</dl></div>
</div>
</div>
<div class="sect1">
<h2 id="_callbacks">Callbacks</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="_websocket_handle_inframe_state_8594_ret">websocket_handle(InFrame, State) → Ret</h3>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 3.1.8
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="color: #009900">Ret</span> <span style="color: #990000">=</span> {<span style="color: #FF6600">ok</span>, <span style="color: #009900">State</span>}
| {<span style="color: #FF6600">ok</span>, <span style="color: #009900">State</span>, <span style="color: #FF6600">hibernate</span>}
| {<span style="color: #FF6600">reply</span>, <span style="color: #009900">OutFrame</span> | [<span style="color: #009900">OutFrame</span>], <span style="color: #009900">State</span>}
| {<span style="color: #FF6600">reply</span>, <span style="color: #009900">OutFrame</span> | [<span style="color: #009900">OutFrame</span>], <span style="color: #009900">State</span>, <span style="color: #FF6600">hibernate</span>}
| {<span style="color: #FF6600">stop</span>, <span style="color: #009900">State</span>}
<span style="color: #009900">InFrame</span> <span style="color: #990000">=</span> {<span style="color: #FF6600">text</span> | <span style="font-weight: bold"><span style="color: #000080">binary</span></span> | <span style="color: #FF6600">ping</span> | <span style="color: #FF6600">pong</span>, <span style="font-weight: bold"><span style="color: #000080">binary</span></span>()}
<span style="color: #009900">State</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">any</span></span>()
<span style="color: #009900">OutFrame</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cow_ws:frame</span></span>()</tt></pre></div></div>
<div class="paragraph"><p>Handle the data received from the Websocket connection.</p></div>
<div class="paragraph"><p>This function will be called every time data is received
from the Websocket connection.</p></div>
<div class="paragraph"><p>The <code>stop</code> return value can be used to close the
connection. A close reply will also result in the connection
being closed.</p></div>
<div class="paragraph"><p>The <code>hibernate</code> option will hibernate the process until
it receives new data from the Websocket connection or an
Erlang message.</p></div>
</div>
<div class="sect2">
<h3 id="_websocket_info_info_state_8594_ret">websocket_info(Info, State) → Ret</h3>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 3.1.8
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="color: #009900">Ret</span> <span style="color: #990000">=</span> {<span style="color: #FF6600">ok</span>, <span style="color: #009900">State</span>}
| {<span style="color: #FF6600">ok</span>, <span style="color: #009900">State</span>, <span style="color: #FF6600">hibernate</span>}
| {<span style="color: #FF6600">reply</span>, <span style="color: #009900">OutFrame</span> | [<span style="color: #009900">OutFrame</span>], <span style="color: #009900">State</span>}
| {<span style="color: #FF6600">reply</span>, <span style="color: #009900">OutFrame</span> | [<span style="color: #009900">OutFrame</span>], <span style="color: #009900">State</span>, <span style="color: #FF6600">hibernate</span>}
| {<span style="color: #FF6600">stop</span>, <span style="color: #009900">State</span>}
<span style="color: #009900">Info</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">any</span></span>()
<span style="color: #009900">State</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">any</span></span>()
<span style="color: #009900">OutFrame</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cow_ws:frame</span></span>()</tt></pre></div></div>
<div class="paragraph"><p>Handle the Erlang message received.</p></div>
<div class="paragraph"><p>This function will be called every time an Erlang message
has been received. The message can be any Erlang term.</p></div>
<div class="paragraph"><p>The <code>stop</code> return value can be used to close the
connection. A close reply will also result in the connection
being closed.</p></div>
<div class="paragraph"><p>The <code>hibernate</code> option will hibernate the process until
it receives another message or new data from the Websocket
connection.</p></div>
</div>
</div>
</div>
</div>
<div class="span3 sidecol">
<h3>
Cowboy
2.0
Function Reference
</h3>
<ul>
<li><a href="/docs/en/cowboy/2.0/guide">User Guide</a></li>
<li><a href="/docs/en/cowboy/2.0/manual">Function Reference</a></li>
</ul>
<h4 id="docs-nav">Navigation</h4>
<h4>Version select</h4>
<ul>
<li><a href="/docs/en/cowboy/1.0/manual">1.0</a></li>
<li><a href="/docs/en/cowboy/2.0/manual">2.0</a></li>
</ul>
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