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255 lines
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<meta name="DC.Title" content="Example: Server program used for sendmsg() and recvmsg()" />
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<meta name="abstract" content="This example shows how to use the sendmsg() API to create a pool of worker jobs." />
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<title>Example: Server program used for sendmsg() and recvmsg()</title>
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<body id="x1descriptors"><a name="x1descriptors"><!-- --></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">Example: Server program used for <span class="apiname">sendmsg()</span> and <span class="apiname">recvmsg()</span></h1>
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<div><p>This example shows how to use the <span class="apiname">sendmsg()</span> API
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to create a pool of worker jobs.</p>
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<div class="section"><div class="note"><span class="notetitle">Note:</span> By using the code examples, you agree to the terms of the <a href="codedisclaimer.htm">Code license and disclaimer information</a>.</div>
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<pre>/**************************************************************************/
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/* Server example that uses sendmsg() to create worker jobs */
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/**************************************************************************/
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/socket.h>
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#include <netinet/in.h>
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#include <spawn.h>
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#define SERVER_PORT 12345
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main (int argc, char *argv[])
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{
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int i, num, pid, rc, on = 1;
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int listen_sd, accept_sd;
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int server_sd, worker_sd, pair_sd[2];
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int spawn_fdmap[1];
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char *spawn_argv[1];
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char *spawn_envp[1];
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struct inheritance inherit;
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struct msghdr msg;
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struct sockaddr_in addr;
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/*************************************************/
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/* If an argument was specified, use it to */
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/* control the number of incoming connections */
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/*************************************************/
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if (argc >= 2)
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num = atoi(argv[1]);
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else
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num = 1;
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/*************************************************/
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/* Create an AF_INET stream socket to receive */
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/* incoming connections on */
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/*************************************************/
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listen_sd = socket(AF_INET, SOCK_STREAM, 0);
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if (listen_sd < 0)
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{
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perror("socket() failed");
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exit(-1);
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}
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/*************************************************/
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/* Allow socket descriptor to be reuseable */
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/*************************************************/
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rc = setsockopt(listen_sd,
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SOL_SOCKET, SO_REUSEADDR,
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(char *)&on, sizeof(on));
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if (rc < 0)
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{
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perror("setsockopt() failed");
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close(listen_sd);
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exit(-1);
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}
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/*************************************************/
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/* Bind the socket */
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/*************************************************/
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memset(&addr, 0, sizeof(addr));
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addr.sin_family = AF_INET;
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addr.sin_addr.s_addr = htonl(INADDR_ANY);
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addr.sin_port = htons(SERVER_PORT);
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rc = bind(listen_sd,
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(struct sockaddr *)&addr, sizeof(addr));
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if (rc < 0)
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{
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perror("bind() failed");
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close(listen_sd);
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exit(-1);
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}
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/*************************************************/
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/* Set the listen back log */
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/*************************************************/
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rc = listen(listen_sd, 5);
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if (rc < 0)
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{
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perror("listen() failed");
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close(listen_sd);
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exit(-1);
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}
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/*************************************************/
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/* Create a pair of UNIX datagram sockets */
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/*************************************************/
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rc = socketpair(AF_UNIX, SOCK_DGRAM, 0, pair_sd);
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if (rc != 0)
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{
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perror("socketpair() failed");
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close(listen_sd);
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exit(-1);
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}
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server_sd = pair_sd[0];
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worker_sd = pair_sd[1];
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/*************************************************/
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/* Initialize parms prior to entering for loop */
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/* */
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/* The worker socket descriptor is mapped to */
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/* descriptor 0 in the child program. */
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/*************************************************/
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memset(&inherit, 0, sizeof(inherit));
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spawn_argv[0] = NULL;
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spawn_envp[0] = NULL;
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spawn_fdmap[0] = worker_sd;
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/*************************************************/
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/* Create each of the worker jobs */
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/*************************************************/
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printf("Creating worker jobs...\n");
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for (i=0; i < num; i++)
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{
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pid = spawn("/QSYS.LIB/QGPL.LIB/WRKR2.PGM",
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1, spawn_fdmap, &inherit,
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spawn_argv, spawn_envp);
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if (pid < 0)
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{
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perror("spawn() failed");
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close(listen_sd);
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close(server_sd);
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close(worker_sd);
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exit(-1);
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}
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printf(" Worker = %d\n", pid);
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}
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/*************************************************/
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/* Close down the worker side of the socketpair */
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/*************************************************/
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close(worker_sd);
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/*************************************************/
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/* Inform the user that the server is ready */
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/*************************************************/
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printf("The server is ready\n");
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/*************************************************/
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/* Go through the loop once for each connection */
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/*************************************************/
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for (i=0; i < num; i++)
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{
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/**********************************************/
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/* Wait for an incoming connection */
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/**********************************************/
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printf("Interation: %d\n", i+1);
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printf(" waiting on accept()\n");
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accept_sd = accept(listen_sd, NULL, NULL);
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if (accept_sd < 0)
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{
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perror("accept() failed");
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close(listen_sd);
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close(server_sd);
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exit(-1);
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}
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printf(" accept completed successfully\n");
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/**********************************************/
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/* Initialize message header structure */
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/**********************************************/
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memset(&msg, 0, sizeof(msg));
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/**********************************************/
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/* We are not sending any data so we do not */
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/* need to set either of the msg_iov fields. */
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/* The memset of the message header structure */
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/* will set the msg_iov pointer to NULL and */
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/* it will set the msg_iovcnt field to 0. */
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/**********************************************/
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/**********************************************/
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/* The only fields in the message header */
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/* structure that need to be filled in are */
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/* the msg_accrights fields. */
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/**********************************************/
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msg.msg_accrights = (char *)&accept_sd;
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msg.msg_accrightslen = sizeof(accept_sd);
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/**********************************************/
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/* Give the incoming connection to one of the */
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/* worker jobs. */
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/* */
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/* NOTE: We do not know which worker job will */
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/* get this inbound connection. */
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/**********************************************/
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rc = sendmsg(server_sd, &msg, 0);
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if (rc < 0)
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{
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perror("sendmsg() failed");
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close(listen_sd);
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close(accept_sd);
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close(server_sd);
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exit(-1);
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}
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printf(" sendmsg completed successfully\n");
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/**********************************************/
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/* Close down the incoming connection since */
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/* it has been given to a worker to handle */
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/**********************************************/
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close(accept_sd);
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}
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/*************************************************/
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/* Close down the server and listen sockets */
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/*************************************************/
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close(server_sd);
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close(listen_sd);
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}</pre>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="xdescriptors.htm" title="The sendmsg() and recvmsg() examples show how to design a server program that uses these APIs to handle incoming connections.">Example: Pass descriptors between processes</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="generic.htm" title="This code example contains the code for a common client job.">Example: Generic client</a></div>
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</div>
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