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<h1 class="lined-header"><span>gun:ping(3)</span></h1>
<h2 id="_name">Name</h2>
<p>gun:ping - Check the health or RTT of the connection</p>
<h2 id="_description">Description</h2>
<div class="listingblock"><div class="content"><!-- Generator: GNU source-highlight 3.1.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><b><font color="#000000">ping</font></b>(<font color="#009900">ConnPid</font>)
<font color="#990000">-></font> <b><font color="#000000">ping</font></b>(<font color="#009900">ConnPid</font>, #{})
<b><font color="#000000">ping</font></b>(<font color="#009900">ConnPid</font>, <font color="#009900">ReqOpts</font>)
<font color="#990000">-></font> <font color="#009900">PingRef</font>
<font color="#009900">ConnPid</font> <font color="#990000">::</font> <b><font color="#000080">pid</font></b>()
<font color="#009900">ReqOpts</font> <font color="#990000">::</font> <b><font color="#000000">gun:req_opts</font></b>()
<font color="#009900">PingRef</font> <font color="#990000">::</font> <b><font color="#000080">reference</font></b>()</tt></pre>
</div></div>
<p>Check the health or round-trip time of the connection.</p>
<p>On protocols that support it, Gun will send a PING frame and wait for its corresponding acknowledgement. When it receives that acknowledgement the user process gets notified via a <code>gun_notify</code> message.</p>
<p>As this happens asynchronously and multiple pings can be sent concurrently, Gun returns a unique reference to the caller that can be used to identify the related acknowledgement.</p>
<p>The following protocols implement PING mechanisms and are supported by this function: HTTP/2.</p>
<p>The following protocols implement PING mechanisms but are not yet supported by this function: HTTP/3 and Websocket. Note that in the case of Websocket, the user can set <code>silence_pings</code> to <code>false</code> and send and receive PING frames.</p>
<p>The following protocols do not implement PING mechanisms: HTTP/1.1, raw and SOCKS5.</p>
<h2 id="_arguments">Arguments</h2>
<dl><dt>ConnPid</dt>
<dd><p>The pid of the Gun connection process.</p>
</dd>
<dt>ReqOpts</dt>
<dd><p>Request options. Only the <code>reply_to</code> and <code>tunnel</code> options are relevant.</p>
</dd>
</dl>
<h2 id="_return_value">Return value</h2>
<p>A reference that identifies the ping is returned. This reference is included in the notification received when a ping ack is received from the server.</p>
<h2 id="_changelog">Changelog</h2>
<ul><li><strong>2.2</strong>: Function introduced.
</li>
</ul>
<h2 id="_examples">Examples</h2>
<div class="listingblock"><div class="title">Send a ping and receive an ack</div>
<div class="content"><!-- Generator: GNU source-highlight 3.1.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><font color="#009900">PingRef</font> <font color="#990000">=</font> <b><font color="#000000">gun:ping</font></b>(<font color="#009900">ConnPid</font>)<font color="#990000">.</font>
{<font color="#FF6600">notify</font>, <font color="#FF6600">ping_ack</font>, <font color="#009900">PingRef</font>} <font color="#990000">=</font> <b><font color="#000000">gun:await</font></b>(<font color="#009900">ConnPid</font>, <font color="#000080">undefined</font>)<font color="#990000">.</font></tt></pre>
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<h2 id="_see_also">See also</h2>
<p><a href="../gun">gun(3)</a>, <a href="../gun.await">gun:await(3)</a>, <a href="../gun_notify">gun_notify(3)</a></p>
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<h3>
Gun
2.2
Function Reference
</h3>
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<li><a href="/docs/en/gun/2.2/manual">Function Reference</a></li>
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<h4>Version select</h4>
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<li><a href="/docs/en/gun/2.0/manual">2.0</a></li>
<li><a href="/docs/en/gun/1.3/manual">1.3</a></li>
<li><a href="/docs/en/gun/1.2/manual">1.2</a></li>
<li><a href="/docs/en/gun/1.1/manual">1.1</a></li>
<li><a href="/docs/en/gun/1.0/manual">1.0</a></li>
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