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<title>socket()--Create Socket</title>
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<h2>socket()--Create Socket</h2>
<div class="box" style="width: 60%;">
<br>
&nbsp;&nbsp;Syntax
<pre>
#include &lt;sys/types.h&gt;
#include &lt;sys/socket.h&gt;
int socket(int <em>address_family</em>,
int <em>type</em>,
int <em>protocol</em>)
</pre>
<br>
&nbsp;&nbsp;Service Program Name: QSOSRV1<br>
<!-- iddvc RMBR -->
<br>
&nbsp;&nbsp;Default Public Authority: *USE<br>
<!-- iddvc RMBR -->
<br>
&nbsp;&nbsp;Threadsafe: Yes<br>
<!-- iddvc RMBR -->
<br>
</div>
<p>The <em>socket()</em> function is used to create an end point for
communications. The end point is represented by the socket descriptor returned
by the <em>socket()</em> function.</p>
<br>
<h3>Parameters</h3>
<dl>
<dt><strong>address_family</strong></dt>
<dd>(Input) The address family to be used with the socket. Supported values
are:
<table cellpadding="5">
<!-- cols="15 85" -->
<tr>
<td align="left" valign="top"><samp>AF_INET</samp></td>
<td align="left" valign="top">For interprocess communications between processes
on the same system or different systems in the Internet domain using the
Internet Protocol (IPv4).</td>
</tr>
<tr>
<td align="left" valign="top"><samp>AF_INET6</samp></td>
<td align="left" valign="top">For interprocess communications between processes
on the same system or different systems in the Internet domain using the
Internet Protocol (IPv6 or IPv4).</td>
</tr>
<tr>
<td align="left" valign="top"><samp>AF_NS</samp></td>
<td align="left" valign="top">For interprocess communications between processes
on the same system or different systems in the domain defined by the Novell or
Xerox protocol definitions.
<p> <strong>Note:</strong> The
<samp>AF_NS</samp> address family is no longer supported as of V5R2.</p>
</td>
</tr>
<tr>
<td align="left" valign="top"><samp>AF_UNIX</samp></td>
<td align="left" valign="top">For interprocess communications between processes
on the same system in the UNIX domain.</td>
</tr>
<tr>
<td align="left" valign="top"><samp>AF_UNIX_CCSID</samp></td>
<td align="left" valign="top">For interprocess communications between processes
on the same system in the UNIX domain using the Qlg_Path_Name_T structure.</td>
</tr>
<tr>
<td align="left" valign="top"><samp>AF_TELEPHONY</samp></td>
<td align="left" valign="top">For interprocess communications between processes
on the same system in the telephony domain.
<p><strong>Note:</strong> The
<samp>AF_TELEPHONY</samp> address family is no longer supported as of V5R3.</p>
</td>
</tr>
</table>
</dd>
<dt><strong>type</strong></dt>
<dd>(Input) The type of communications desired. Supported values are:<br>
<br>
<table cellpadding="5">
<!-- cols="15 85" -->
<tr>
<td align="left" valign="top"><samp>SOCK_DGRAM</samp></td>
<td align="left" valign="top">Indicates a datagram socket is desired.</td>
</tr>
<tr>
<td align="left" valign="top"><samp>SOCK_SEQPACKET</samp></td>
<td align="left" valign="top">Indicates a full-duplex sequenced packet socket
is desired. Each input and output operation consists of exactly one
record.</td>
</tr>
<tr>
<td align="left" valign="top"><samp>SOCK_STREAM</samp></td>
<td align="left" valign="top">Indicates a full-duplex stream socket is
desired.</td>
</tr>
<tr>
<td align="left" valign="top"><samp>SOCK_RAW</samp></td>
<td align="left" valign="top">Indicates communication is directly to the
network protocols. A process must have the appropriate privilege
<samp>*ALLOBJ</samp> to use this type of socket. Used by users who want to
access the lower-level protocols directly.</td>
</tr>
</table>
<br>
<br>
</dd>
<dt><strong>protocol</strong></dt>
<dd>(Input) The protocol to be used on the socket. Supported values are:<br>
<br>
<table cellpadding="5">
<!-- cols="15 85" -->
<tr>
<td align="left" valign="top">0</td>
<td align="left" valign="top">Indicates that the default protocol for the
<em>type</em> selected is to be used. For example, <samp>IPPROTO_TCP</samp> is
chosen for the protocol if the <em>type</em> was set to
<samp>SOCK_STREAM</samp> and the address family is <samp>AF_INET</samp>.</td>
</tr>
<tr>
<td align="left" valign="top"><samp>IPPROTO_IP</samp></td>
<td align="left" valign="top">Equivalent to specifying the value zero (0).</td>
</tr>
<tr>
<td align="left" valign="top"><samp>IPPROTO_TCP</samp></td>
<td align="left" valign="top">Indicates that the TCP protocol is to be
used.</td>
</tr>
<tr>
<td align="left" valign="top"><samp>IPPROTO_UDP</samp></td>
<td align="left" valign="top">Indicates that the UDP protocol is to be
used.</td>
</tr>
<tr>
<td align="left" valign="top"><samp>IPPROTO_RAW</samp></td>
<td align="left" valign="top">Indicates that communications is to the IP
layer.</td>
</tr>
<tr>
<td align="left" valign="top"><samp>IPPROTO_ICMP</samp></td>
<td align="left" valign="top">Indicates that the Internet Control Message
Protocol (ICMP) is to be used.</td>
</tr>
<tr>
<td align="left" valign="top"><samp>IPPROTO_ICMPV6</samp></td>
<td align="left" valign="top">Indicates that the Internet Control Message
Protocol (ICMPv6) is to be used.</td>
</tr>
<tr>
<td align="left" valign="top"><samp>TELPROTO_TEL</samp></td>
<td align="left" valign="top">Equivalent to specifying the value zero (0).</td>
</tr>
</table>
<br>
<br>
</dd>
</dl>
<p><strong>Note:</strong> When the <em>type</em> is <samp>SOCK_RAW</samp>, the
<em>protocol</em> can be set to some predefined protocol number from 0-255. See
<a href="#HDRSCKUS">Usage Notes</a> for further details.</p>
<br>
<h3>Authorities</h3>
<p>When the SOCKET being created is of type SOCK_RAW, the thread must have
*ALLOBJ special authority. When the thread does not have this authority, the
EACCES is returned for <em>errno</em>.</p>
<br>
<h3>Return Value</h3>
<p><em>socket()</em> returns an integer. Possible values are:</p>
<ul>
<li>-1 (unsuccessful)</li>
<li>n (successful), where n is a socket descriptor.</li>
</ul>
<br>
<h3>Error Conditions</h3>
<p>When <em>socket()</em> fails, <em>errno</em> can be set to one of the
following:</p>
<table cellpadding="5">
<!-- cols="25 75" -->
<tr>
<td align="left" valign="top"><em>[EACCES]</em></td>
<td align="left" valign="top">Permission denied.
<p>Process does not have the appropriate privileges to create the socket with
the specified type or protocol.</p>
</td>
</tr>
<tr>
<td align="left" valign="top"><em>[EAFNOSUPPORT]</em></td>
<td align="left" valign="top">The type of socket is not supported in this
protocol family.<br>
<br>
</td>
</tr>
<tr>
<td align="left" valign="top"><em>[EIO]</em></td>
<td align="left" valign="top">Input/output error.<br>
<br>
</td>
</tr>
<tr>
<td align="left" valign="top"><em>[EMFILE]</em></td>
<td align="left" valign="top">Too many descriptions for this process.<br>
<br>
</td>
</tr>
<tr>
<td align="left" valign="top"><em>[ENFILE]</em></td>
<td align="left" valign="top">Too many descriptions in system.<br>
<br>
</td>
</tr>
<tr>
<td align="left" valign="top"><em>[ENOBUFS]</em></td>
<td align="left" valign="top">There is not enough buffer space for the
requested operation.<br>
<br>
</td>
</tr>
<tr>
<td align="left" valign="top"><em>[EPROTOTYPE]</em></td>
<td align="left" valign="top">The socket type or protocols are not compatible.
<br>
<br>
</td>
</tr>
<tr>
<td align="left" valign="top"><em>[EPROTONOSUPPORT]</em></td>
<td align="left" valign="top">No protocol of the specified type and domain
exists.<br>
<br>
</td>
</tr>
<tr>
<td align="left" valign="top"><em>[ESOCKTNOSUPPORT]</em></td>
<td align="left" valign="top">The specified socket type is not supported.<br>
<br>
</td>
</tr>
<tr>
<td align="left" valign="top"><em>[EUNATCH]</em></td>
<td align="left" valign="top">The protocol required to support the specified
address family is not available at this time.<br>
<br>
</td>
</tr>
<tr>
<td align="left" valign="top"><em>[EUNKNOWN]</em></td>
<td align="left" valign="top">Unknown system state.</td>
</tr>
</table>
<br>
<br>
<h3>Error Messages</h3>
<table width="100%" cellpadding="5">
<!-- cols="15 85" -->
<tr>
<th align="left" valign="top" nowrap>Message ID</th>
<th align="left" valign="top">Error Message Text</th>
</tr>
<tr>
<td align="left" valign="top">CPE3418 E</td>
<td align="left" valign="top">Possible APAR condition or hardware failure.</td>
</tr>
<tr>
<td align="left" valign="top">CPF9872 E</td>
<td align="left" valign="top">Program or service program &amp;1 in library
&amp;2 ended. Reason code &amp;3.</td>
</tr>
<tr>
<td align="left" valign="top">CPFA081 E</td>
<td align="left" valign="top">Unable to set return value or error code.</td>
</tr>
</table>
<br>
<br>
<h3><a name="HDRSCKUS">Usage Notes</a></h3>
<ol>
<li>The socket address families and types supported by sockets are defined in
<strong>&lt;sys/socket.h&gt;</strong>. The protocols are defined in
<strong>&lt;netinet/in.h&gt;</strong> (Internet protocols).<br>
<br>
</li>
<li>The <samp>AF_UNIX</samp> and <samp>AF_UNIX_CCSID</samp> address family
supports a protocol of 0 for both <samp>SOCK_STREAM</samp> and
<samp>SOCK_DGRAM</samp>.<br>
<br>
</li>
<li> The <samp>AF_NS</samp>
address family is no longer supported as of V5R2.<br>
<br>
</li>
<li>The following tables list the combinations of types and protocols that are
supported for <samp>AF_INET</samp> and the combinations of types and protocols
that are supported for <samp>AF_INET6</samp>.<br><br>
<table border cellpadding="5">
<!-- cols="15 85" -->
<tr>
<th align="left" valign="top" colspan="2"><em><a name="#TBLSOCKCOM">Supported
Combinations of Types and Protocols for <samp>AF_INET</samp></a></em></th>
</tr>
<tr>
<th align="left" valign="top">Socket Type</th>
<th align="left" valign="top">Protocol</th>
</tr>
<tr>
<td align="left" valign="top">STREAM</td>
<td align="left" valign="top"><samp>IPPROTO_TCP</samp> (see Usage note 5)</td>
</tr>
<tr>
<td align="left" valign="top">DGRAM</td>
<td align="left" valign="top"><samp>IPPROTO_UDP</samp> </td>
</tr>
<tr>
<td align="left" valign="top">RAW</td>
<td align="left" valign="top"><samp>IPPROTO_RAW</samp>,
<samp>IPPROTO_ICMP</samp>, <em>protocol_number</em>, (see Usage note 6)</td>
</tr>
</table>
<br>
<br>
<table border cellpadding="5">
<!-- cols="15 85" -->
<tr>
<th align="left" valign="top" colspan="2"><em><a name="TBLSOCKCOM6">Supported
Combinations of Types and Protocols for <samp>AF_INET6</samp></a></em></th>
</tr>
<tr>
<th align="left" valign="top">Socket Type</th>
<th align="left" valign="top">Protocol</th>
</tr>
<tr>
<td align="left" valign="top">STREAM</td>
<td align="left" valign="top"><samp>IPPROTO_TCP</samp> </td>
</tr>
<tr>
<td align="left" valign="top">DGRAM</td>
<td align="left" valign="top"><samp>IPPROTO_UDP</samp> </td>
</tr>
<tr>
<td align="left" valign="top">RAW</td>
<td align="left" valign="top"><samp>IPPROTO_RAW</samp>,
<samp>IPPROTO_ICMPV6</samp>, <em>protocol_number</em>, (see Usage note 6)</td>
</tr>
</table>
<br>
<br>
</li>
<li>The <strong>ALWANYNET</strong> (Allow ANYNET support) network attribute
allows a customer to select whether a SNA transport can be used for AF_INET
socket applications.
<p>The system administrator can see the current status of the
<strong>ALWANYNET</strong> attribute and can change that status. (This can be
done by using the Display Network Attributes (DSPNETA) and Change Network
Attributes (CHGNETA) commands, respectively.)</p>
<p>If the status is changed, the change takes effect immediately. Also, the
state of the <strong>ALWANYNET</strong> stays the same across IPLs. For
example, if the current status is *YES and the system administrator changes the
value to *NO, the use of <samp>AF_INET</samp> over a transport other than
TCP/IP is deactivated. If a system IPL is performed after this point, the use
of <samp>AF_INET</samp> over a SNA transport remains deactivated after the
system IPL.</p>
<p>If AF_INET sockets will only be used over a TCP/IP transport, the
<strong>ALWANYNET</strong> status should be set to *NO to improve CPU
utilization.</p>
<p><strong>Note:</strong> If you are also using APPC over TCP/IP
<strong>ALWANYNET</strong> status needs to be set to *YES.</p>
</li>
<li>When the socket type is <samp>SOCK_RAW</samp>, you can specify any protocol
number between 0-255. Two exceptions are the <samp>IPPROTO_TCP</samp> and
<samp>IPPROTO_UDP</samp> protocols, which cannot be specified on a socket type
of <samp>SOCK_RAW</samp> (if you issue <em>socket()</em>, you get an error with
an error code of <samp>[EPROTONOSUPPORT]</samp>). Each raw socket is associated
with one IP protocol number, and receives all data for that protocol. For
example, if two processes create a raw socket with the same protocol number,
and data is received for the protocol, then both processes get copies of the
data.
<p>Protocol numbers 0 (<samp>IPPROTO_IP</samp>) and 255
(<samp>IPPROTO_RAW</samp>) have some unique characteristics. If a protocol
number of zero is specified, then IP sends all data received from all the
protocol numbers (except <samp>IPPROTO_TCP</samp> and <samp>IPPROTO_UDP</samp>
protocols). If a protocol number of 255 is specified, a user must ensure that
the IP header data is included in the data sent out on an output operation.</p>
</li>
<li>The <samp>AF_TELEPHONY</samp>
address family is no longer supported as of V5R3.
</li>
</ol>
<br>
<h3>Related Information</h3>
<ul>
<li><a href="socketp.htm">socketpair()</a>--Create a Pair of Sockets</li>
</ul>
<br>
<hr>
API introduced: V3R1
<hr>
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