1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>websocket::stream::async_handshake (1 of 2 overloads)</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="../async_handshake.html" title="websocket::stream::async_handshake"> 9<link rel="prev" href="../async_handshake.html" title="websocket::stream::async_handshake"> 10<link rel="next" href="overload2.html" title="websocket::stream::async_handshake (2 of 2 overloads)"> 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="../async_handshake.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../async_handshake.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="overload2.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h6 class="title"> 27<a name="beast.ref.boost__beast__websocket__stream.async_handshake.overload1"></a><a class="link" href="overload1.html" title="websocket::stream::async_handshake (1 of 2 overloads)">websocket::stream::async_handshake 28 (1 of 2 overloads)</a> 29</h6></div></div></div> 30<p> 31 Perform the WebSocket handshake asynchronously in the client role. 32 </p> 33<h7><a name="beast.ref.boost__beast__websocket__stream.async_handshake.overload1.h0"></a> 34 <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_handshake.overload1.synopsis"></a></span><a class="link" href="overload1.html#beast.ref.boost__beast__websocket__stream.async_handshake.overload1.synopsis">Synopsis</a> 35 </h7><pre class="programlisting"><span class="keyword">template</span><span class="special"><</span> 36 <span class="keyword">class</span> <span class="identifier">HandshakeHandler</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> 37<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> 38<span class="identifier">async_handshake</span><span class="special">(</span> 39 <span class="identifier">string_view</span> <span class="identifier">host</span><span class="special">,</span> 40 <span class="identifier">string_view</span> <span class="identifier">target</span><span class="special">,</span> 41 <span class="identifier">HandshakeHandler</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> 42</pre> 43<h7><a name="beast.ref.boost__beast__websocket__stream.async_handshake.overload1.h1"></a> 44 <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_handshake.overload1.description"></a></span><a class="link" href="overload1.html#beast.ref.boost__beast__websocket__stream.async_handshake.overload1.description">Description</a> 45 </h7><p> 46 This initiating function is used to asynchronously begin performing the 47 <a href="https://en.wikipedia.org/wiki/WebSocket#Protocol_handshake" target="_top">WebSocket 48 handshake</a>, required before messages can be sent and received. 49 During the handshake, the client sends the Websocket Upgrade HTTP request, 50 and the server replies with an HTTP response indicating the result of 51 the handshake. This call always returns immediately. The asynchronous 52 operation will continue until one of the following conditions is true: 53 </p> 54<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 55<li class="listitem"> 56 The request is sent and the response is received. 57 </li> 58<li class="listitem"> 59 An error occurs. 60 </li> 61</ul></div> 62<p> 63 The algorithm, known as a <span class="emphasis"><em>composed asynchronous operation</em></span>, 64 is implemented in terms of calls to the next layer's <code class="computeroutput"><span class="identifier">async_read_some</span></code> 65 and <code class="computeroutput"><span class="identifier">async_write_some</span></code> 66 functions. No other operation may be performed on the stream until this 67 operation completes. The handshake is successful if the received HTTP 68 response indicates the upgrade was accepted by the server, represented 69 by a <a href="https://tools.ietf.org/html/rfc7230#section-3.1.2" target="_top">status-code</a> 70 of <a class="link" href="../../boost__beast__http__status.html" title="http::status"><code class="computeroutput"><span class="identifier">beast</span><span class="special">::</span><span class="identifier">http</span><span class="special">::</span><span class="identifier">status</span><span class="special">::</span><span class="identifier">switching_protocols</span></code></a>. 71 </p> 72<h7><a name="beast.ref.boost__beast__websocket__stream.async_handshake.overload1.h2"></a> 73 <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_handshake.overload1.parameters"></a></span><a class="link" href="overload1.html#beast.ref.boost__beast__websocket__stream.async_handshake.overload1.parameters">Parameters</a> 74 </h7><div class="informaltable"><table class="table"> 75<colgroup> 76<col> 77<col> 78</colgroup> 79<thead><tr> 80<th> 81 <p> 82 Name 83 </p> 84 </th> 85<th> 86 <p> 87 Description 88 </p> 89 </th> 90</tr></thead> 91<tbody> 92<tr> 93<td> 94 <p> 95 <code class="computeroutput"><span class="identifier">host</span></code> 96 </p> 97 </td> 98<td> 99 <p> 100 The name of the remote host. This is required by the HTTP protocol 101 to set the "Host" header field. The implementation 102 will not access the string data after the initiating function 103 returns. 104 </p> 105 </td> 106</tr> 107<tr> 108<td> 109 <p> 110 <code class="computeroutput"><span class="identifier">target</span></code> 111 </p> 112 </td> 113<td> 114 <p> 115 The request-target, in origin-form. The server may use the 116 target to distinguish different services on the same listening 117 port. The implementation will not access the string data after 118 the initiating function returns. 119 </p> 120 </td> 121</tr> 122<tr> 123<td> 124 <p> 125 <code class="computeroutput"><span class="identifier">handler</span></code> 126 </p> 127 </td> 128<td> 129 <p> 130 The completion handler to invoke when the operation completes. 131 The implementation takes ownership of the handler by performing 132 a decay-copy. The equivalent function signature of the handler 133 must be: 134 </p> 135<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> 136 <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> 137<span class="special">);</span> 138</pre> 139 <p> 140 Regardless of whether the asynchronous operation completes 141 immediately or not, the handler will not be invoked from within 142 this function. Invocation of the handler will be performed 143 in a manner equivalent to using <code class="computeroutput"><span class="identifier">net</span><span class="special">::</span><span class="identifier">post</span></code>. 144 </p> 145 </td> 146</tr> 147</tbody> 148</table></div> 149<h7><a name="beast.ref.boost__beast__websocket__stream.async_handshake.overload1.h3"></a> 150 <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_handshake.overload1.example"></a></span><a class="link" href="overload1.html#beast.ref.boost__beast__websocket__stream.async_handshake.overload1.example">Example</a> 151 </h7><pre class="programlisting"><span class="identifier">ws</span><span class="special">.</span><span class="identifier">async_handshake</span><span class="special">(</span><span class="string">"localhost"</span><span class="special">,</span> <span class="string">"/"</span><span class="special">,</span> 152 <span class="special">[](</span><span class="identifier">error_code</span> <span class="identifier">ec</span><span class="special">)</span> 153 <span class="special">{</span> 154 <span class="keyword">if</span><span class="special">(</span><span class="identifier">ec</span><span class="special">)</span> 155 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cerr</span> <span class="special"><<</span> <span class="string">"Error: "</span> <span class="special"><<</span> <span class="identifier">ec</span><span class="special">.</span><span class="identifier">message</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"\n"</span><span class="special">;</span> 156 <span class="special">});</span> 157</pre> 158<h7><a name="beast.ref.boost__beast__websocket__stream.async_handshake.overload1.h4"></a> 159 <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_handshake.overload1.see_also"></a></span><a class="link" href="overload1.html#beast.ref.boost__beast__websocket__stream.async_handshake.overload1.see_also">See 160 Also</a> 161 </h7><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 162<li class="listitem"> 163 <a href="https://tools.ietf.org/html/rfc6455#section-4.1" target="_top">Websocket 164 Opening Handshake Client Requirements (RFC6455)</a> 165 </li> 166<li class="listitem"> 167 <a href="https://tools.ietf.org/html/rfc7230#section-5.4" target="_top">Host 168 field (RFC7230)</a> 169 </li> 170<li class="listitem"> 171 <a href="https://tools.ietf.org/html/rfc7230#section-3.1.1" target="_top">request-target 172 (RFC7230)</a> 173 </li> 174<li class="listitem"> 175 <a href="https://tools.ietf.org/html/rfc7230#section-5.3.1" target="_top">origin-form 176 (RFC7230)</a> 177 </li> 178</ul></div> 179</div> 180<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 181<td align="left"></td> 182<td align="right"><div class="copyright-footer">Copyright © 2016-2019 Vinnie 183 Falco<p> 184 Distributed under the Boost Software License, Version 1.0. (See accompanying 185 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>) 186 </p> 187</div></td> 188</tr></table> 189<hr> 190<div class="spirit-nav"> 191<a accesskey="p" href="../async_handshake.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../async_handshake.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="overload2.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 192</div> 193</body> 194</html> 195
