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| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="boost_asio.reference.basic_raw_socket.cancel.overload2"></a><a class="link" href="overload2.html" title="basic_raw_socket::cancel (2 of 2 overloads)">basic_raw_socket::cancel |
| (2 of 2 overloads)</a> |
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| <p> |
| <span class="emphasis"><em>Inherited from basic_socket.</em></span> |
| </p> |
| <p> |
| Cancel all asynchronous operations associated with the socket. |
| </p> |
| <pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">system</span><span class="special">::</span><span class="identifier">error_code</span> <span class="identifier">cancel</span><span class="special">(</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">system</span><span class="special">::</span><span class="identifier">error_code</span> <span class="special">&</span> <span class="identifier">ec</span><span class="special">);</span> |
| </pre> |
| <p> |
| This function causes all outstanding asynchronous connect, send and receive |
| operations to finish immediately, and the handlers for cancelled operations |
| 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> |
| error. |
| </p> |
| <a name="boost_asio.reference.basic_raw_socket.cancel.overload2.parameters"></a><h6> |
| <a name="id952304"></a> |
| <a class="link" href="overload2.html#boost_asio.reference.basic_raw_socket.cancel.overload2.parameters">Parameters</a> |
| </h6> |
| <div class="variablelist"> |
| <p class="title"><b></b></p> |
| <dl> |
| <dt><span class="term">ec</span></dt> |
| <dd><p> |
| Set to indicate what error occurred, if any. |
| </p></dd> |
| </dl> |
| </div> |
| <a name="boost_asio.reference.basic_raw_socket.cancel.overload2.remarks"></a><h6> |
| <a name="id952310"></a> |
| <a class="link" href="overload2.html#boost_asio.reference.basic_raw_socket.cancel.overload2.remarks">Remarks</a> |
| </h6> |
| <p> |
| Calls to <code class="computeroutput"><span class="identifier">cancel</span><span class="special">()</span></code> |
| 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> |
| when run on Windows XP, Windows Server 2003, and earlier versions of |
| Windows, unless BOOST_ASIO_ENABLE_CANCELIO is defined. However, the CancelIo |
| function has two issues that should be considered before enabling its |
| use: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| It will only cancel asynchronous operations that were initiated in |
| the current thread. |
| </li> |
| <li class="listitem"> |
| It can appear to complete without error, but the request to cancel |
| the unfinished operations may be silently ignored by the operating |
| system. Whether it works or not seems to depend on the drivers that |
| are installed. |
| </li> |
| </ul></div> |
| <p> |
| For portable cancellation, consider using one of the following alternatives: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| Disable asio's I/O completion port backend by defining BOOST_ASIO_DISABLE_IOCP. |
| </li> |
| <li class="listitem"> |
| Use the <code class="computeroutput"><span class="identifier">close</span><span class="special">()</span></code> |
| function to simultaneously cancel the outstanding operations and |
| close the socket. |
| </li> |
| </ul></div> |
| <p> |
| When running on Windows Vista, Windows Server 2008, and later, the CancelIoEx |
| function is always used. This function does not have the problems described |
| above. |
| </p> |
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| <td align="right"><div class="copyright-footer">Copyright © 2003 - 2010 Christopher M. Kohlhoff<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| 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>) |
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