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  26 <div class="titlepage"><div><div><h5 class="title">
  27 <a name="beast.ref.boost__beast__websocket__stream.async_pong"></a><a class="link" href="async_pong.html" title="websocket::stream::async_pong">websocket::stream::async_pong</a>
  28 </h5></div></div></div>
  29 <p>
  30           <a class="indexterm" name="idm45873472875248"></a>
  31 Send a websocket pong control frame asynchronously.
  32         </p>
  33 <h6>
  34 <a name="beast.ref.boost__beast__websocket__stream.async_pong.h0"></a>
  35           <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_pong.synopsis"></a></span><a class="link" href="async_pong.html#beast.ref.boost__beast__websocket__stream.async_pong.synopsis">Synopsis</a>
  36         </h6>
  37 <pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span>
  38     <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">&lt;</span><span class="identifier">executor_type</span><span class="special">&gt;&gt;</span>
  39 <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>
  40 <span class="identifier">async_pong</span><span class="special">(</span>
  41     <span class="identifier">ping_data</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">payload</span><span class="special">,</span>
  42     <span class="identifier">WriteHandler</span><span class="special">&amp;&amp;</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">&lt;</span> <span class="identifier">executor_type</span> <span class="special">&gt;{});</span>
  43 </pre>
  44 <h6>
  45 <a name="beast.ref.boost__beast__websocket__stream.async_pong.h1"></a>
  46           <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_pong.description"></a></span><a class="link" href="async_pong.html#beast.ref.boost__beast__websocket__stream.async_pong.description">Description</a>
  47         </h6>
  48 <p>
  49           This function is used to asynchronously send a <a href="https://tools.ietf.org/html/rfc6455#section-5.5.3" target="_top">pong
  50           frame</a>, which is usually sent automatically in response to a ping
  51           frame from the remote peer.
  52         </p>
  53 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
  54 <li class="listitem">
  55               The pong frame is written.
  56             </li>
  57 <li class="listitem">
  58               An error occurs.
  59             </li>
  60 </ul></div>
  61 <p>
  62           The algorithm, known as a <span class="emphasis"><em>composed asynchronous operation</em></span>,
  63           is implemented in terms of calls to the next layer's <code class="computeroutput"><span class="identifier">async_write_some</span></code>
  64           function. The program must ensure that no other calls to <a class="link" href="ping.html" title="websocket::stream::ping"><code class="computeroutput"><span class="identifier">websocket</span><span class="special">::</span><span class="identifier">stream</span><span class="special">::</span><span class="identifier">ping</span></code></a>, <a class="link" href="pong.html" title="websocket::stream::pong"><code class="computeroutput"><span class="identifier">websocket</span><span class="special">::</span><span class="identifier">stream</span><span class="special">::</span><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">websocket</span><span class="special">::</span><span class="identifier">stream</span><span class="special">::</span><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">websocket</span><span class="special">::</span><span class="identifier">stream</span><span class="special">::</span><span class="identifier">async_pong</span></code></a> are performed until
  65           this operation completes. If a close frame is sent or received before the
  66           pong frame is sent, the error received by this completion handler will
  67           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>. WebSocket allows pong
  68           frames to be sent at any time, without first receiving a ping. An unsolicited
  69           pong sent in this fashion may indicate to the remote peer that the connection
  70           is still active.
  71         </p>
  72 <h6>
  73 <a name="beast.ref.boost__beast__websocket__stream.async_pong.h2"></a>
  74           <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_pong.parameters"></a></span><a class="link" href="async_pong.html#beast.ref.boost__beast__websocket__stream.async_pong.parameters">Parameters</a>
  75         </h6>
  76 <div class="informaltable"><table class="table">
  77 <colgroup>
  78 <col>
  79 <col>
  80 </colgroup>
  81 <thead><tr>
  82 <th>
  83                   <p>
  84                     Name
  85                   </p>
  86                 </th>
  87 <th>
  88                   <p>
  89                     Description
  90                   </p>
  91                 </th>
  92 </tr></thead>
  93 <tbody>
  94 <tr>
  95 <td>
  96                   <p>
  97                     <code class="computeroutput"><span class="identifier">payload</span></code>
  98                   </p>
  99                 </td>
 100 <td>
 101                   <p>
 102                     The payload of the pong message, which may be empty. The implementation
 103                     will not access the contents of this object after the initiating
 104                     function returns.
 105                   </p>
 106                 </td>
 107 </tr>
 108 <tr>
 109 <td>
 110                   <p>
 111                     <code class="computeroutput"><span class="identifier">handler</span></code>
 112                   </p>
 113                 </td>
 114 <td>
 115                   <p>
 116                     The completion handler to invoke when the operation completes.
 117                     The implementation takes ownership of the handler by performing
 118                     a decay-copy. The equivalent function signature of the handler
 119                     must be:
 120                   </p>
 121 <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>
 122     <span class="identifier">error_code</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">ec</span>     <span class="comment">// Result of operation</span>
 123 <span class="special">);</span>
 124 </pre>
 125                   <p>
 126                     Regardless of whether the asynchronous operation completes immediately
 127                     or not, the handler will not be invoked from within this function.
 128                     Invocation of the handler will be performed in a manner equivalent
 129                     to using <code class="computeroutput"><span class="identifier">net</span><span class="special">::</span><span class="identifier">post</span></code>.
 130                   </p>
 131                 </td>
 132 </tr>
 133 </tbody>
 134 </table></div>
 135 </div>
 136 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 137 <td align="left"></td>
 138 <td align="right"><div class="copyright-footer">Copyright &#169; 2016-2019 Vinnie
 139       Falco<p>
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