Example: Server program to create a pool of multiple accept() worker jobs

/**************************************************************************/
/* Server example creates a pool of worker jobs with multiple accept()    */
/**************************************************************************/

#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    spawn_fdmap[1];
   char  *spawn_argv[1];
   char  *spawn_envp[1];
   struct inheritance   inherit;
   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);
   }

   /*************************************************/
   /* Initialize parms prior to entering for loop   */
   /*                                               */
   /* The listen 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] = listen_sd;

   /*************************************************/
   /* Create each of the worker jobs                */
   /*************************************************/
   printf("Creating worker jobs...\n");
   for (i=0; i < num; i++)
   {
      pid = spawn("/QSYS.LIB/QGPL.LIB/WRKR4.PGM",
                  1, spawn_fdmap, &inherit,
                  spawn_argv, spawn_envp);
      if (pid < 0)
      {
         perror("spawn() failed");
         close(listen_sd);
         exit(-1);
      }
      printf("  Worker = %d\n", pid);
   }

   /*************************************************/
   /* Inform the user that the server is ready      */
   /*************************************************/
   printf("The server is ready\n");

   /*************************************************/
   /* Close down the listening socket               */
   /*************************************************/
   close(listen_sd);
}