1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>websocket::stream::async_ping</title> 5<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../../index.html" title="Chapter 1. Boost.Beast"> 8<link rel="up" href="../boost__beast__websocket__stream.html" title="websocket::stream"> 9<link rel="prev" href="ping/overload2.html" title="websocket::stream::ping (2 of 2 overloads)"> 10<link rel="next" href="pong.html" title="websocket::stream::pong"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="ping/overload2.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../boost__beast__websocket__stream.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="pong.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h5 class="title"> 27<a name="beast.ref.boost__beast__websocket__stream.async_ping"></a><a class="link" href="async_ping.html" title="websocket::stream::async_ping">websocket::stream::async_ping</a> 28</h5></div></div></div> 29<p> 30 <a class="indexterm" name="idm46057518695824"></a> 31 </p> 32<p> 33 Send a websocket ping control frame asynchronously. 34 </p> 35<h6> 36<a name="beast.ref.boost__beast__websocket__stream.async_ping.h0"></a> 37 <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_ping.synopsis"></a></span><a class="link" href="async_ping.html#beast.ref.boost__beast__websocket__stream.async_ping.synopsis">Synopsis</a> 38 </h6> 39<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span> 40 <span class="keyword">class</span> <a href="../../../../../../../doc/html/boost_asio/reference/WriteHandler.html" target="_top"><span class="emphasis"><em>WriteHandler</em></span></a> <span class="special">=</span> <span class="identifier">net</span><span class="special">::</span><span class="identifier">default_completion_token_t</span><span class="special"><</span><a class="link" href="executor_type.html" title="websocket::stream::executor_type">executor_type</a><span class="special">>></span> 41<a href="../../../../../../../doc/html/boost_asio/reference/asynchronous_operations.html#boost_asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type" target="_top"><span class="emphasis"><em>DEDUCED</em></span></a> 42<span class="identifier">async_ping</span><span class="special">(</span> 43 <span class="identifier">ping_data</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">payload</span><span class="special">,</span> 44 <span class="identifier">WriteHandler</span><span class="special">&&</span> <span class="identifier">handler</span> <span class="special">=</span> <span class="identifier">net</span><span class="special">::</span><span class="identifier">default_completion_token_t</span><span class="special"><</span> <a class="link" href="executor_type.html" title="websocket::stream::executor_type">executor_type</a> <span class="special">>{});</span> 45</pre> 46<h6> 47<a name="beast.ref.boost__beast__websocket__stream.async_ping.h1"></a> 48 <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_ping.description"></a></span><a class="link" href="async_ping.html#beast.ref.boost__beast__websocket__stream.async_ping.description">Description</a> 49 </h6> 50<p> 51 This function is used to asynchronously send a <a href="https://tools.ietf.org/html/rfc6455#section-5.5.2" target="_top">ping 52 frame</a>, which usually elicits an automatic pong control frame response 53 from the peer. 54 </p> 55<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 56<li class="listitem"> 57 The ping frame is written. 58 </li> 59<li class="listitem"> 60 An error occurs. 61 </li> 62</ul></div> 63<p> 64 The algorithm, known as a <span class="emphasis"><em>composed asynchronous operation</em></span>, 65 is implemented in terms of calls to the next layer's <code class="computeroutput"><span class="identifier">async_write_some</span></code> 66 function. The program must ensure that no other calls to <a class="link" href="ping/overload1.html" title="websocket::stream::ping (1 of 2 overloads)"><code class="computeroutput"><span class="identifier">ping</span></code></a>, <a class="link" href="pong/overload1.html" title="websocket::stream::pong (1 of 2 overloads)"><code class="computeroutput"><span class="identifier">pong</span></code></a>, <a class="link" href="async_ping.html" title="websocket::stream::async_ping"><code class="computeroutput"><span class="identifier">async_ping</span></code></a>, or <a class="link" href="async_pong.html" title="websocket::stream::async_pong"><code class="computeroutput"><span class="identifier">async_pong</span></code></a> are performed until 67 this operation completes. If a close frame is sent or received before the 68 ping frame is sent, the error received by this completion handler will 69 be <code class="computeroutput"><span class="identifier">net</span><span class="special">::</span><span class="identifier">error</span><span class="special">::</span><span class="identifier">operation_aborted</span></code>. 70 </p> 71<h6> 72<a name="beast.ref.boost__beast__websocket__stream.async_ping.h2"></a> 73 <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_ping.parameters"></a></span><a class="link" href="async_ping.html#beast.ref.boost__beast__websocket__stream.async_ping.parameters">Parameters</a> 74 </h6> 75<div class="informaltable"><table class="table"> 76<colgroup> 77<col> 78<col> 79</colgroup> 80<thead><tr> 81<th> 82 <p> 83 Name 84 </p> 85 </th> 86<th> 87 <p> 88 Description 89 </p> 90 </th> 91</tr></thead> 92<tbody> 93<tr> 94<td> 95 <p> 96 <code class="computeroutput"><span class="identifier">payload</span></code> 97 </p> 98 </td> 99<td> 100 <p> 101 The payload of the ping message, which may be empty. The implementation 102 will not access the contents of this object after the initiating 103 function returns. 104 </p> 105 </td> 106</tr> 107<tr> 108<td> 109 <p> 110 <code class="computeroutput"><span class="identifier">handler</span></code> 111 </p> 112 </td> 113<td> 114 <p> 115 The completion handler to invoke when the operation completes. 116 The implementation takes ownership of the handler by performing 117 a decay-copy. The equivalent function signature of the handler 118 must be: 119 </p> 120<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">void</span> <span class="identifier">handler</span><span class="special">(</span> 121 <span class="identifier">error_code</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">ec</span> <span class="comment">// Result of operation</span> 122<span class="special">);</span> 123</pre> 124 <p> 125 Regardless of whether the asynchronous operation completes immediately 126 or not, the handler will not be invoked from within this function. 127 Invocation of the handler will be performed in a manner equivalent 128 to using <code class="computeroutput"><span class="identifier">net</span><span class="special">::</span><span class="identifier">post</span></code>. 129 </p> 130 </td> 131</tr> 132</tbody> 133</table></div> 134</div> 135<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 136<td align="left"></td> 137<td align="right"><div class="copyright-footer">Copyright © 2016-2019 Vinnie 138 Falco<p> 139 Distributed under the Boost Software License, Version 1.0. (See accompanying 140 file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) 141 </p> 142</div></td> 143</tr></table> 144<hr> 145<div class="spirit-nav"> 146<a accesskey="p" href="ping/overload2.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../boost__beast__websocket__stream.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="pong.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 147</div> 148</body> 149</html> 150
