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<body class="manpage">
<div id="header">
<h1>
nn_recvmsg(3) Manual Page
</h1>
<h2>NAME</h2>
<div class="sectionbody">
<p>nn_recvmsg -
fine-grained alternative to nn_recv
</p>
</div>
</div>
<div id="content">
<div class="sect1">
<h2 id="_synopsis">SYNOPSIS</h2>
<div class="sectionbody">
<div class="paragraph"><p><strong>#include &lt;nanomsg/nn.h&gt;</strong></p></div>
<div class="paragraph"><p><strong>NN_EXPORT int nn_recvmsg (int <em>s</em>, struct nn_msghdr <em>*msghdr</em>, int <em>flags</em>);</strong></p></div>
</div>
</div>
<div class="sect1">
<h2 id="_description">DESCRIPTION</h2>
<div class="sectionbody">
<div class="paragraph"><p>Receives a message from socket <em>s</em> into buffers specified by <em>msghdr</em> parameter
along with any additional control data. <em>msghdr</em> parameter should be nullified
before being used.</p></div>
<div class="paragraph"><p>Structure <em>nn_msghdr</em> contains at least following members:</p></div>
<div class="literalblock">
<div class="content">
<pre><tt>struct nn_iovec *msg_iov;
int msg_iovlen;
void *msg_control;
size_t msg_controllen;</tt></pre>
</div></div>
<div class="paragraph"><p><em>msg_iov</em> points to a gather array of buffers to fill in. <em>msg_iovlen</em> specifies
the size of the array.</p></div>
<div class="paragraph"><p><em>msg_control</em> points to the buffer to hold control information associated with
the received message. <em>msg_controllen</em> specifies the length of the buffer.
If the control information should not be retrieved, set <em>msg_control</em> parameter
to NULL. For detailed discussion of how to parse the control information check
<a href="nn_cmsg.3.html">nn_cmsg(3)</a> man page.</p></div>
<div class="paragraph"><p>Structure <em>nn_iovec</em> defines one element in the gather array (a buffer to be
filled in by message data) and contains following members:</p></div>
<div class="literalblock">
<div class="content">
<pre><tt>void *iov_base;
size_t iov_len;</tt></pre>
</div></div>
<div class="paragraph"><p>Alternatively, <em>nanomsg</em> library can allocate the buffer for you. To do so,
let the <em>iov_base</em> point to void* variable to receive the buffer and set
<em>iov_len</em> to <em>NN_MSG</em>. After successful completion user is responsible
for deallocating the message using <a href="nn_freemsg.3.html">nn_freemsg(3)</a> function. Gather
array in <em>nn_msghdr</em> structure can contain only one element in this case.</p></div>
<div class="paragraph"><p>The <em>flags</em> argument is a combination of the flags defined below:</p></div>
<div class="dlist"><dl>
<dt class="hdlist1">
<strong>NN_DONTWAIT</strong>
</dt>
<dd>
<p>
Specifies that the operation should be performed in non-blocking mode. If the
message cannot be received straight away, the function will fail with <em>errno</em>
set to EAGAIN.
</p>
</dd>
</dl></div>
</div>
</div>
<div class="sect1">
<h2 id="_return_value">RETURN VALUE</h2>
<div class="sectionbody">
<div class="paragraph"><p>If the function succeeds number of bytes in the message is returned. Otherwise,
-1 is returned and <em>errno</em> is set to to one of the values defined
below.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_errors">ERRORS</h2>
<div class="sectionbody">
<div class="dlist"><dl>
<dt class="hdlist1">
<strong>EBADF</strong>
</dt>
<dd>
<p>
The provided socket is invalid.
</p>
</dd>
<dt class="hdlist1">
<strong>ENOTSUP</strong>
</dt>
<dd>
<p>
The operation is not supported by this socket type.
</p>
</dd>
<dt class="hdlist1">
<strong>EFSM</strong>
</dt>
<dd>
<p>
The operation cannot be performed on this socket at the moment because socket is
not in the appropriate state. This error may occur with socket types that
switch between several states.
</p>
</dd>
<dt class="hdlist1">
<strong>EAGAIN</strong>
</dt>
<dd>
<p>
Non-blocking mode was requested and there&#8217;s no message to receive at the moment.
</p>
</dd>
<dt class="hdlist1">
<strong>EINTR</strong>
</dt>
<dd>
<p>
The operation was interrupted by delivery of a signal before the message was
received.
</p>
</dd>
<dt class="hdlist1">
<strong>ETIMEDOUT</strong>
</dt>
<dd>
<p>
Individual socket types may define their own specific timeouts. If such timeout
is hit this error will be returned.
</p>
</dd>
<dt class="hdlist1">
<strong>ETERM</strong>
</dt>
<dd>
<p>
The library is terminating.
</p>
</dd>
</dl></div>
</div>
</div>
<div class="sect1">
<h2 id="_example">EXAMPLE</h2>
<div class="sectionbody">
<div class="listingblock">
<div class="content">
<pre><tt>struct nn_msghdr hdr;
struct nn_iovec iov [2];
char buf0 [4];
char buf1 [2];
iov [0].iov_base = buf0;
iov [0].iov_len = sizeof (buf0);
iov [1].iov_base = buf1;
iov [1].iov_len = sizeof (buf1);
memset (&amp;hdr, 0, sizeof (hdr));
hdr.msg_iov = iov;
hdr.msg_iovlen = 2;
nn_recvmsg (s, &amp;hdr, 0);</tt></pre>
</div></div>
</div>
</div>
<div class="sect1">
<h2 id="_see_also">SEE ALSO</h2>
<div class="sectionbody">
<div class="paragraph"><p><a href="nn_recv.3.html">nn_recv(3)</a>
<a href="nn_sendmsg.3.html">nn_sendmsg(3)</a>
<a href="nn_allocmsg.3.html">nn_allocmsg(3)</a>
<a href="nn_freemsg.3.html">nn_freemsg(3)</a>
<a href="nn_cmsg.3.html">nn_cmsg(3)</a>
<a href="nanomsg.7.html">nanomsg(7)</a></p></div>
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<h2 id="_authors">AUTHORS</h2>
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<div class="paragraph"><p>Martin Sustrik &lt;<a href="mailto:sustrik@250bpm.com">sustrik@250bpm.com</a>&gt;</p></div>
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nanomsg 0.5-beta<br />
Last updated 2014-11-14 22:43:29 CET
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