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<h1 class="topictitle1">Example: Server program used for <span class="apiname">sendmsg()</span> and <span class="apiname">recvmsg()</span></h1>
<div><p>This example shows how to use the <span class="apiname">sendmsg()</span> API
to create a pool of worker jobs.</p>
<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>
<pre>/**************************************************************************/
/* Server example that uses sendmsg() to create worker jobs */
/**************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <spawn.h>
#define SERVER_PORT 12345
main (int argc, char *argv[])
{
int i, num, pid, rc, on = 1;
int listen_sd, accept_sd;
int server_sd, worker_sd, pair_sd[2];
int spawn_fdmap[1];
char *spawn_argv[1];
char *spawn_envp[1];
struct inheritance inherit;
struct msghdr msg;
struct sockaddr_in addr;
/*************************************************/
/* If an argument was specified, use it to */
/* control the number of incoming connections */
/*************************************************/
if (argc >= 2)
num = atoi(argv[1]);
else
num = 1;
/*************************************************/
/* Create an AF_INET stream socket to receive */
/* incoming connections on */
/*************************************************/
listen_sd = socket(AF_INET, SOCK_STREAM, 0);
if (listen_sd < 0)
{
perror("socket() failed");
exit(-1);
}
/*************************************************/
/* Allow socket descriptor to be reuseable */
/*************************************************/
rc = setsockopt(listen_sd,
SOL_SOCKET, SO_REUSEADDR,
(char *)&on, sizeof(on));
if (rc < 0)
{
perror("setsockopt() failed");
close(listen_sd);
exit(-1);
}
/*************************************************/
/* Bind the socket */
/*************************************************/
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = htonl(INADDR_ANY);
addr.sin_port = htons(SERVER_PORT);
rc = bind(listen_sd,
(struct sockaddr *)&addr, sizeof(addr));
if (rc < 0)
{
perror("bind() failed");
close(listen_sd);
exit(-1);
}
/*************************************************/
/* Set the listen back log */
/*************************************************/
rc = listen(listen_sd, 5);
if (rc < 0)
{
perror("listen() failed");
close(listen_sd);
exit(-1);
}
/*************************************************/
/* Create a pair of UNIX datagram sockets */
/*************************************************/
rc = socketpair(AF_UNIX, SOCK_DGRAM, 0, pair_sd);
if (rc != 0)
{
perror("socketpair() failed");
close(listen_sd);
exit(-1);
}
server_sd = pair_sd[0];
worker_sd = pair_sd[1];
/*************************************************/
/* Initialize parms prior to entering for loop */
/* */
/* The worker socket descriptor is mapped to */
/* descriptor 0 in the child program. */
/*************************************************/
memset(&inherit, 0, sizeof(inherit));
spawn_argv[0] = NULL;
spawn_envp[0] = NULL;
spawn_fdmap[0] = worker_sd;
/*************************************************/
/* Create each of the worker jobs */
/*************************************************/
printf("Creating worker jobs...\n");
for (i=0; i < num; i++)
{
pid = spawn("/QSYS.LIB/QGPL.LIB/WRKR2.PGM",
1, spawn_fdmap, &inherit,
spawn_argv, spawn_envp);
if (pid < 0)
{
perror("spawn() failed");
close(listen_sd);
close(server_sd);
close(worker_sd);
exit(-1);
}
printf(" Worker = %d\n", pid);
}
/*************************************************/
/* Close down the worker side of the socketpair */
/*************************************************/
close(worker_sd);
/*************************************************/
/* Inform the user that the server is ready */
/*************************************************/
printf("The server is ready\n");
/*************************************************/
/* Go through the loop once for each connection */
/*************************************************/
for (i=0; i < num; i++)
{
/**********************************************/
/* Wait for an incoming connection */
/**********************************************/
printf("Interation: %d\n", i+1);
printf(" waiting on accept()\n");
accept_sd = accept(listen_sd, NULL, NULL);
if (accept_sd < 0)
{
perror("accept() failed");
close(listen_sd);
close(server_sd);
exit(-1);
}
printf(" accept completed successfully\n");
/**********************************************/
/* Initialize message header structure */
/**********************************************/
memset(&msg, 0, sizeof(msg));
/**********************************************/
/* We are not sending any data so we do not */
/* need to set either of the msg_iov fields. */
/* The memset of the message header structure */
/* will set the msg_iov pointer to NULL and */
/* it will set the msg_iovcnt field to 0. */
/**********************************************/
/**********************************************/
/* The only fields in the message header */
/* structure that need to be filled in are */
/* the msg_accrights fields. */
/**********************************************/
msg.msg_accrights = (char *)&accept_sd;
msg.msg_accrightslen = sizeof(accept_sd);
/**********************************************/
/* Give the incoming connection to one of the */
/* worker jobs. */
/* */
/* NOTE: We do not know which worker job will */
/* get this inbound connection. */
/**********************************************/
rc = sendmsg(server_sd, &msg, 0);
if (rc < 0)
{
perror("sendmsg() failed");
close(listen_sd);
close(accept_sd);
close(server_sd);
exit(-1);
}
printf(" sendmsg completed successfully\n");
/**********************************************/
/* Close down the incoming connection since */
/* it has been given to a worker to handle */
/**********************************************/
close(accept_sd);
}
/*************************************************/
/* Close down the server and listen sockets */
/*************************************************/
close(server_sd);
close(listen_sd);
}</pre>
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<div class="familylinks">
<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 class="relref"><strong>Related reference</strong><br />
<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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