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---
version: tip
layout: manpage_v2
title: nn_recv(3compat)
---
<h1>nn_recv(3compat)</h1>
<div class="sect1">
<h2 id="_name">NAME</h2>
<div class="sectionbody">
<div class="paragraph">
<p>nn_recv - receive data (compatible API)</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_synopsis">SYNOPSIS</h2>
<div class="sectionbody">
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c"><span></span><span class="tok-cp">#include</span><span class="tok-w"> </span><span class="tok-cpf"><nanomsg/nn.h></span>
<span class="tok-kt">int</span><span class="tok-w"> </span><span class="tok-n">nn_recv</span><span class="tok-p">(</span><span class="tok-kt">int</span><span class="tok-w"> </span><span class="tok-n">sock</span><span class="tok-p">,</span><span class="tok-w"> </span><span class="tok-kt">void</span><span class="tok-w"> </span><span class="tok-o">*</span><span class="tok-n">data</span><span class="tok-p">,</span><span class="tok-w"> </span><span class="tok-kt">size_t</span><span class="tok-w"> </span><span class="tok-n">size</span><span class="tok-p">,</span><span class="tok-w"> </span><span class="tok-kt">int</span><span class="tok-w"> </span><span class="tok-n">flags</span><span class="tok-p">)</span></code></pre>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_description">DESCRIPTION</h2>
<div class="sectionbody">
<div class="paragraph">
<p>The <code>nn_recv()</code> function receives a message from the socket <em>sock</em>.
The message body must fit within <em>size</em> bytes, and will be stored
at the location specified by <em>data</em>, unless <em>size</em> is the
special value <code>NN_MSG</code>, indicating a zero-copy operation.</p>
</div>
<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<i class="fa icon-note" title="Note"></i>
</td>
<td class="content">
This function is provided for API
<a href="nng_compat.3compat.html">compatibility</a> with legacy <em>libnanomsg</em>.
Consider using the relevant <a href="libnng.3.html">modern API</a> instead.
</td>
</tr>
</table>
</div>
<div class="paragraph">
<p>If <em>size</em> has the special value <code>NN_MSG</code>, then a zero-copy operation
is performed.
In this case, instead of copying the message data into the address
specified by <em>data</em>, a new message large enough to hold the message data
will be allocated (as if by the
function <a href="nn_allocmsg.3compat.html"><code>nn_allocmsg()</code></a>), and the message
payload will be stored accordingly.
In this case, the value stored at <em>data</em> will not be message data,
but a pointer to the message itself.
In this case, on success, the caller shall take responsibility for
the final disposition of the message (such as by sending it to
another peer using <a href="nn_send.3compat.html"><code>nn_send()</code></a>) or
<a href="nn_freemsg.3compat.html"><code>nn_freemsg()</code></a>.</p>
</div>
<div class="paragraph">
<p>The <em>flags</em> field may contain the special flag <code>NN_DONTWAIT</code>.
In this case, if the no message is available for immediate receipt,
the operation shall not block, but instead will fail with the error <code>EAGAIN</code>.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_return_values">RETURN VALUES</h2>
<div class="sectionbody">
<div class="paragraph">
<p>This function returns the number of bytes sent on success, and -1 on error.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_errors">ERRORS</h2>
<div class="sectionbody">
<div class="hdlist">
<table>
<tr>
<td class="hdlist1">
<code>EAGAIN</code>
</td>
<td class="hdlist2">
<p>The operation would block.</p>
</td>
</tr>
<tr>
<td class="hdlist1">
<code>EBADF</code>
</td>
<td class="hdlist2">
<p>The socket <em>sock</em> is not open.</p>
</td>
</tr>
<tr>
<td class="hdlist1">
<code>EFSM</code>
</td>
<td class="hdlist2">
<p>The socket cannot receive in this state.</p>
</td>
</tr>
<tr>
<td class="hdlist1">
<code>ENOTSUP</code>
</td>
<td class="hdlist2">
<p>This protocol cannot receive.</p>
</td>
</tr>
<tr>
<td class="hdlist1">
<code>ETIMEDOUT</code>
</td>
<td class="hdlist2">
<p>Operation timed out.</p>
</td>
</tr>
</table>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_see_also">SEE ALSO</h2>
<div class="sectionbody">
<div class="paragraph text-left">
<p><a href="nn_errno.3compat.html">nn_errno(3compat)</a>,
<a href="nn_recvmsg.3compat.html">nn_recvmsg(3compat)</a>,
<a href="nn_send.3compat.html">nn_send(3compat)</a>,
<a href="nn_socket.3compat.html">nn_socket(3compat)</a>,
<a href="nng_compat.3compat.html">nn_compat(3compat)</a>,
<a href="nng.7.html">nng(7)</a></p>
</div>
</div>
</div>
|
