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<div id="header">
<h1>nn_sendmsg(3compat) Manual Page</h1>
<div id="toc" class="toc2">
<div id="toctitle">Table of Contents</div>
<ul class="sectlevel1">
<li><a href="#_synopsis">SYNOPSIS</a></li>
<li><a href="#_description">DESCRIPTION</a></li>
<li><a href="#_return_values">RETURN VALUES</a></li>
<li><a href="#_errors">ERRORS</a></li>
<li><a href="#_see_also">SEE ALSO</a></li>
</ul>
</div>
<h2 id="_name">NAME</h2>
<div class="sectionbody">
<p>nn_sendmsg - send message (compatible API)</p>
</div>
</div>
<div id="content">
<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-cpf"><nanomsg/nn.h></span><span class="tok-cp"></span>
<span class="tok-kt">int</span> <span class="tok-nf">nn_sendmsg</span><span class="tok-p">(</span><span class="tok-kt">int</span> <span class="tok-n">sock</span><span class="tok-p">,</span> <span class="tok-k">const</span> <span class="tok-k">struct</span> <span class="tok-n">nn_msghdr</span> <span class="tok-o">*</span><span class="tok-n">hdr</span><span class="tok-p">,</span> <span class="tok-kt">int</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_sendmsg()</code> function sends the message described by <em>hdr</em> using the
socket <em>sock</em>.</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>The <em>flags</em> field may contain the special flag <code>NN_DONTWAIT</code>.
In this case, if the socket is unable to accept more data for sending,
the operation shall not block, but instead will fail with the error <code>EAGAIN</code>.</p>
</div>
<div class="paragraph">
<p>The <em>hdr</em> points to a structure of type <code>struct nn_msghdr</code>, which has the
following definition:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c"><span></span><span class="tok-k">struct</span> <span class="tok-n">nn_iovec</span> <span class="tok-p">{</span>
<span class="tok-kt">void</span> <span class="tok-o">*</span> <span class="tok-n">iov_base</span><span class="tok-p">;</span>
<span class="tok-kt">size_t</span> <span class="tok-n">iov_len</span><span class="tok-p">;</span>
<span class="tok-p">};</span>
<span class="tok-k">struct</span> <span class="tok-n">nn_msghdr</span> <span class="tok-p">{</span>
<span class="tok-k">struct</span> <span class="tok-n">nn_iovec</span> <span class="tok-o">*</span><span class="tok-n">msg_iov</span><span class="tok-p">;</span>
<span class="tok-kt">int</span> <span class="tok-n">msg_iovlen</span><span class="tok-p">;</span>
<span class="tok-kt">void</span> <span class="tok-o">*</span> <span class="tok-n">msg_control</span><span class="tok-p">;</span>
<span class="tok-kt">size_t</span> <span class="tok-n">msg_controllen</span><span class="tok-p">;</span>
<span class="tok-p">};</span></code></pre>
</div>
</div>
<div class="paragraph">
<p>The <code>msg_iov</code> is an array of gather items, permitting the message
to be spread into different memory blocks.
There are <code>msg_iovlen</code> elements in this array, each of which
has the base address (<code>iov_base</code>) and length (<code>iov_len</code>) indicated.</p>
</div>
<div class="paragraph">
<p>For buffers allocated for zero copy
(such as by <a href="nn_allocmsg.3compat.html"><code>nn_allocmsg()</code></a>), the value
of <code>iov_base</code> should be the address of the pointer to the buffer,
rather than the address of the buffer itself.
In this case, the value of <code>iov_len</code> should be <code>NN_MSG</code>,
as the length is inferred from the allocated message.
If the <code>msg_iovlen</code> field is <code>NN_MSG</code>, then this function will free
the associated buffer after it is done with it, if it returns successfully.
(If the function returns with an error, then the caller retains ownership
of the associated buffer and may retry the operation or free the buffer
at its choice.)</p>
</div>
<div class="paragraph">
<p>The values of <code>msg_control</code> and <code>msg_controllen</code> describe a buffer
of ancillary data to send the message.
This is currently only useful to provide the message headers
used with <a href="nng.7.html#raw_mode">raw mode</a> sockets.
In all other circumstances these fields should be zero.
Details about this structure are covered in
<a href="nn_cmsg.3compat.html"><code>nn_cmsg(3compat)</code></a>.</p>
</div>
<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<i class="fa icon-note" title="Note"></i>
</td>
<td class="content">
The send operation is performed asynchronously, and may not have
completed before this function returns control to the caller.
</td>
</tr>
</table>
</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 send in this state.</p>
</td>
</tr>
<tr>
<td class="hdlist1">
<code>EINVAL</code>
</td>
<td class="hdlist2">
<p>The <em>hdr</em> is invalid.</p>
</td>
</tr>
<tr>
<td class="hdlist1">
<code>ENOTSUP</code>
</td>
<td class="hdlist2">
<p>This protocol cannot send.</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_cmsg.3compat.html">nn_cmsg(3compat)</a>,
<a href="nn_errno.3compat.html">nn_errno(3compat)</a>,
<a href="nn_recv.3compat.html">nn_recv(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>
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