156 lines
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HTML
156 lines
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<?xml version="1.0" encoding="UTF-8"?>
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<meta name="DC.Title" content="Use AF_UNIX_CCSID address family" />
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<meta name="abstract" content="AF_UNIX_CCSID address family sockets have the same specifications as AF_UNIX address family sockets. They can be used for connection-oriented or connectionless and provide communications on the same system." />
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<meta name="description" content="AF_UNIX_CCSID address family sockets have the same specifications as AF_UNIX address family sockets. They can be used for connection-oriented or connectionless and provide communications on the same system." />
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<meta name="copyright" content="(C) Copyright IBM Corporation 2001, 2006" />
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<title>Use AF_UNIX_CCSID address family</title>
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</head>
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<body id="uafunixccsid"><a name="uafunixccsid"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Use AF_UNIX_CCSID address family</h1>
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<div><p>AF_UNIX_CCSID address family sockets have the same specifications
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as AF_UNIX address family sockets. They can be used for connection-oriented
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or connectionless and provide communications on the same system.</p>
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<div class="section"><p>Before
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working with AF_UNIX_CCSID socket application, you should be familiar with
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the <strong>Qlg_Path_Name_T</strong> structure to determine the output format.</p>
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<p>When working with an output address structure, such as one returned from <span class="apiname">accept()</span>, <span class="apiname">getsockname()</span>, <span class="apiname">getpeername()</span>, <span class="apiname">recvfrom()</span>, and <span class="apiname">recvmsg()</span>,
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the application must examine the socket address structure (sockaddr_unc) to
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determine its format. The sunc_format and sunc_qlg fields determine the output
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format of the path name. But sockets do not necessarily use the same values
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on output as the application used on input addresses. </p>
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<p><br /><img src="rzab6503.gif" alt="Socket flow of events used in server and client AF_UNIX_CCSID address family example programs." /><br /></p>
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</div>
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<div class="section"><h4 class="sectiontitle">Socket flow of events: Server application that uses AF_UNIX_CCSID
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address family</h4><p>The first example uses the following sequence of
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function calls:</p>
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<ol><li>The <span class="apiname">socket()</span> function returns a socket descriptor representing
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an endpoint. The statement also identifies that the UNIX_CCSID address family
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with the stream transport (SOCK_STREAM) are used for this socket. You can
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also use the <span class="apiname">socketpair()</span> function to initialize a UNIX<sup>®</sup> socket.
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<p>AF_UNIX or AF_UNIX_CCSID are the only address families to support the <span class="apiname">socketpair()</span> function.
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The <span class="apiname">socketpair()</span> function returns two socket descriptors
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that are unnamed and connected.</p>
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</li>
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<li>After the socket descriptor is created, the <span class="apiname">bind()</span> function
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gets a unique name for the socket. <p>The name space for UNIX domain sockets
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consists of path names. When a sockets program calls the <span class="apiname">bind()</span> function,
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an entry is created in the file system directory. If the path name already
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exists, the <span class="apiname">bind()</span> fails. Thus, a UNIX domain socket
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program should always call an <span class="apiname">unlink()</span> functions to remove
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the directory entry when it ends. </p>
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</li>
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<li>The <span class="apiname">listen()</span> allows the server to accept incoming
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client connections. In this example, the backlog is set to 10. This means
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that the system queues 10 incoming connection requests before the system starts
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rejecting the incoming requests.</li>
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<li>The server uses the <span class="apiname">accept()</span> function to accept an
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incoming connection request. The <span class="apiname">accept()</span> call blocks indefinitely
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waiting for the incoming connection to arrive.</li>
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<li>The <span class="apiname">recv()</span> function receives data
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from the client application. In this example, the client sends 250 bytes of
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data over. Thus the SO_RCVLOWAT socket option can be used, specifying that <span class="apiname">recv()</span> is
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not required to wake up until all 250 bytes of data have arrived.</li>
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<li>The <span class="apiname">send()</span> function echoes the data back to the client.</li>
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<li>The <span class="apiname">close()</span> function closes any open socket descriptors.</li>
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<li>The <span class="apiname">unlink()</span> function removes the UNIX path name
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from the file system.</li>
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</ol>
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</div>
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<div class="section"><h4 class="sectiontitle">Socket flow of events: Client application that uses AF_UNIX_CCSID
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address family</h4><p>The second example uses the following sequence of
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function calls:</p>
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<ol><li>The <span class="apiname">socket()</span> function returns a socket descriptor representing
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an endpoint. The statement also identifies that the UNIX address family
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with the stream transport (SOCK_STREAM) is used for this socket. The function
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returns a socket descriptor representing an endpoint. You can also use the <span class="apiname">socketpair()</span> function
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to initialize a UNIX socket. <p>AF_UNIX or AF_UNIX_CCSID are the only
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address families to support the <span class="apiname">socketpair()</span> function.
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The <span class="apiname">socketpair()</span> function returns two socket descriptors
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that are unnamed and connected.</p>
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</li>
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<li>After the socket descriptor is received, the <span class="apiname">connect()</span> function
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is used to establish a connection to the server.</li>
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<li>The <span class="apiname">send()</span> function sends 250 bytes of data that are
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specified in the server application with the SO_RCVLOWAT socket
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option. </li>
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<li>The <span class="apiname">recv()</span> function loops until all 250 bytes of the
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data have arrived. </li>
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<li>The <span class="apiname">close()</span> function closes any open socket descriptors.</li>
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</ol>
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</div>
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</div>
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<div>
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<ul class="ullinks">
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<li class="ulchildlink"><strong><a href="xafunixccsidsrv.htm">Example: Server application that uses AF_UNIX_CCSID address family</a></strong><br />
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The sample programs use the AF_UNIX_CCSID address family.</li>
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<li class="ulchildlink"><strong><a href="xafunixccsidcl.htm">Example: Client application that uses AF_UNIX_CCSID address family</a></strong><br />
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The sample programs use the AF_UNIX_CCSID address family.</li>
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</ul>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="uaddrfam.htm" title="This topic includes sample programs that illustrate each of the socket address families.">Design applications with address families</a></div>
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</div>
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<div class="relref"><strong>Related reference</strong><br />
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<div><a href="cafunixccsid.htm" title="The AF_UNIX_CCSID family is compatible with the AF_UNIX address family and has the same limitations.">AF_UNIX_CCSID address family</a></div>
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<div><a href="uafunix.htm" title="The AF_UNIX address family (sockets using the AF_UNIX or AF_UNIX_CCSID address families) can be connection-oriented (type SOCK_STREAM) or they can be connectionless (type SOCK_DGRAM).">Use AF_UNIX address family</a></div>
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</div>
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<div class="relinfo"><strong>Related information</strong><br />
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<div><a href="../apiref/pns.htm">Path name format</a></div>
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<div><a href="../apis/recvfr.htm">recvfrom()</a></div>
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<div><a href="../apis/accept.htm">accept()</a></div>
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<div><a href="../apis/gpeern.htm">getpeername()</a></div>
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<div><a href="../apis/gsockn.htm">getsockname()</a></div>
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<div><a href="../apis/recvms.htm">recvmsg()</a></div>
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<div><a href="../apis/close.htm">close()</a></div>
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<div><a href="../apis/socket.htm">socket()</a></div>
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<div><a href="../apis/bind.htm">bind()</a></div>
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<div><a href="../apis/unlink.htm">unlink()</a></div>
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<div><a href="../apis/listen.htm">listen()</a></div>
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<div><a href="../apis/send.htm">send()</a></div>
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<div><a href="../apis/connec.htm">connect()</a></div>
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<div><a href="../apis/recv.htm">recv()</a></div>
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<div><a href="../apis/socketp.htm">socketpair()</a></div>
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</div>
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</div>
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</body>
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</html>
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