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<title>basic_raw_socket::cancel (1 of 2 overloads)</title>
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<div class="titlepage"><div><div><h5 class="title">
<a name="boost_asio.reference.basic_raw_socket.cancel.overload1"></a><a class="link" href="overload1.html" title="basic_raw_socket::cancel (1 of 2 overloads)">basic_raw_socket::cancel
(1 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">void cancel();
</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">boost::asio::error::operation_aborted</code>
error.
</p>
<h6>
<a name="boost_asio.reference.basic_raw_socket.cancel.overload1.h0"></a>
<span class="phrase"><a name="boost_asio.reference.basic_raw_socket.cancel.overload1.exceptions"></a></span><a class="link" href="overload1.html#boost_asio.reference.basic_raw_socket.cancel.overload1.exceptions">Exceptions</a>
</h6>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<dt><span class="term">boost::system::system_error</span></dt>
<dd><p>
Thrown on failure.
</p></dd>
</dl>
</div>
<h6>
<a name="boost_asio.reference.basic_raw_socket.cancel.overload1.h1"></a>
<span class="phrase"><a name="boost_asio.reference.basic_raw_socket.cancel.overload1.remarks"></a></span><a class="link" href="overload1.html#boost_asio.reference.basic_raw_socket.cancel.overload1.remarks">Remarks</a>
</h6>
<p>
Calls to <code class="computeroutput">cancel()</code> will always fail with <code class="computeroutput">boost::asio::error::operation_not_supported</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" style="list-style-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" style="list-style-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">close()</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 © 2003-2018 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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