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<div class="titlepage"><div><div><h3 class="title">
<a name="asio.reference.synchronous_socket_operations"></a><a class="link" href="synchronous_socket_operations.html" title="Requirements on synchronous socket operations">Requirements
on synchronous socket operations</a>
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<p>
In this section, <span class="emphasis"><em>synchronous socket operations</em></span> are those
member functions specified as two overloads, with and without an argument
of type <code class="computeroutput"><span class="identifier">error_code</span><span class="special">&amp;</span></code>:
</p>
<pre class="programlisting"><span class="bold"><strong><span class="emphasis"><em>R f</em></span></strong></span><span class="special">(</span><span class="emphasis"><em><span class="bold"><strong>A1</strong></span></em></span> <span class="identifier">a1</span><span class="special">,</span> <span class="emphasis"><em><span class="bold"><strong>A2</strong></span></em></span> <span class="identifier">a2</span><span class="special">,</span> <span class="special">...,</span> <span class="emphasis"><em><span class="bold"><strong>AN</strong></span></em></span> <span class="identifier">aN</span><span class="special">);</span>
<span class="bold"><strong><span class="emphasis"><em>R f</em></span></strong></span><span class="special">(</span><span class="emphasis"><em><span class="bold"><strong>A1</strong></span></em></span> <span class="identifier">a1</span><span class="special">,</span> <span class="emphasis"><em><span class="bold"><strong>A2</strong></span></em></span> <span class="identifier">a2</span><span class="special">,</span> <span class="special">...,</span> <span class="emphasis"><em><span class="bold"><strong>AN</strong></span></em></span> <span class="identifier">aN</span><span class="special">,</span> <span class="identifier">error_code</span><span class="special">&amp;</span> <span class="identifier">ec</span><span class="special">);</span>
</pre>
<p>
For an object <code class="computeroutput"><span class="identifier">s</span></code>, the conditions
under which its synchronous socket operations may block the calling thread
(C++Std [defns.block]) are determined as follows.
</p>
<p>
If:
</p>
<p>
<code class="computeroutput"><span class="identifier">s</span><span class="special">.</span><span class="identifier">non_blocking</span><span class="special">()</span>
<span class="special">==</span> <span class="keyword">true</span></code>,
</p>
<p>
— the synchronous socket operation is specified in terms of a <span class="emphasis"><em>POSIX</em></span>
function other than <code class="computeroutput"><a href="http://www.opengroup.org/onlinepubs/9699919799/functions/poll.html" target="_top"><code class="computeroutput"><span class="identifier">poll</span><span class="special">()</span></code></a></code>,
</p>
<p>
— that <span class="emphasis"><em>POSIX</em></span> function lists <code class="computeroutput"><span class="identifier">EWOULDBLOCK</span></code>
or <code class="computeroutput"><span class="identifier">EAGAIN</span></code> in its failure
conditions, and
</p>
<p>
— the effects of the operation cannot be established immediately
</p>
<p>
then the synchronous socket operation shall not block the calling thread.
[<span class="emphasis"><em>Note:</em></span> And the effects of the operation are not established.
<span class="emphasis"><em>end note</em></span>]
</p>
<p>
Otherwise, the synchronous socket operation shall block the calling thread
until the effects are established.
</p>
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<div class="copyright-footer">Copyright © 2003-2023 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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