doc/html/boost_asio/reference/basic_socket_streambuf/cancel/overload1.html

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  27 <a name="boost_asio.reference.basic_socket_streambuf.cancel.overload1"></a><a class="link" href="overload1.html" title="basic_socket_streambuf::cancel (1 of 2 overloads)">basic_socket_streambuf::cancel
  28           (1 of 2 overloads)</a>
  29 </h5></div></div></div>
  30 <p>
  31             <span class="emphasis"><em>Inherited from basic_socket.</em></span>
  32           </p>
  33 <p>
  34             Cancel all asynchronous operations associated with the socket.
  35           </p>
  36 <pre class="programlisting"><span class="keyword">void</span> <span class="identifier">cancel</span><span class="special">();</span>
  37 </pre>
  38 <p>
  39             This function causes all outstanding asynchronous connect, send and receive
  40             operations to finish immediately, and the handlers for cancelled operations
  41             will be passed the <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">error</span><span class="special">::</span><span class="identifier">operation_aborted</span></code>
  42             error.
  43           </p>
  44 <h6>
  45 <a name="boost_asio.reference.basic_socket_streambuf.cancel.overload1.h0"></a>
  46             <span class="phrase"><a name="boost_asio.reference.basic_socket_streambuf.cancel.overload1.exceptions"></a></span><a class="link" href="overload1.html#boost_asio.reference.basic_socket_streambuf.cancel.overload1.exceptions">Exceptions</a>
  47           </h6>
  48 <div class="variablelist">
  49 <p class="title"><b></b></p>
  50 <dl class="variablelist">
  51 <dt><span class="term">boost::system::system_error</span></dt>
  52 <dd><p>
  53                   Thrown on failure.
  54                 </p></dd>
  55 </dl>
  56 </div>
  57 <h6>
  58 <a name="boost_asio.reference.basic_socket_streambuf.cancel.overload1.h1"></a>
  59             <span class="phrase"><a name="boost_asio.reference.basic_socket_streambuf.cancel.overload1.remarks"></a></span><a class="link" href="overload1.html#boost_asio.reference.basic_socket_streambuf.cancel.overload1.remarks">Remarks</a>
  60           </h6>
  61 <p>
  62             Calls to <code class="computeroutput"><span class="identifier">cancel</span><span class="special">()</span></code>
  63             will always fail with <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">error</span><span class="special">::</span><span class="identifier">operation_not_supported</span></code>
  64             when run on Windows XP, Windows Server 2003, and earlier versions of
  65             Windows, unless BOOST_ASIO_ENABLE_CANCELIO is defined. However, the CancelIo
  66             function has two issues that should be considered before enabling its
  67             use:
  68           </p>
  69 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
  70 <li class="listitem">
  71                 It will only cancel asynchronous operations that were initiated in
  72                 the current thread.
  73               </li>
  74 <li class="listitem">
  75                 It can appear to complete without error, but the request to cancel
  76                 the unfinished operations may be silently ignored by the operating
  77                 system. Whether it works or not seems to depend on the drivers that
  78                 are installed.
  79               </li>
  80 </ul></div>
  81 <p>
  82             For portable cancellation, consider using one of the following alternatives:
  83           </p>
  84 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
  85 <li class="listitem">
  86                 Disable asio's I/O completion port backend by defining BOOST_ASIO_DISABLE_IOCP.
  87               </li>
  88 <li class="listitem">
  89                 Use the <code class="computeroutput"><span class="identifier">close</span><span class="special">()</span></code>
  90                 function to simultaneously cancel the outstanding operations and
  91                 close the socket.
  92               </li>
  93 </ul></div>
  94 <p>
  95             When running on Windows Vista, Windows Server 2008, and later, the CancelIoEx
  96             function is always used. This function does not have the problems described
  97             above.
  98           </p>
  99 </div>
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