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Code Sample:A Connection-Oriented Example - listen(), accept()

Beginners Guide to Sockets

(Continued from previous question...)

Code Sample:A Connection-Oriented Example - listen(), accept() 

/* Generic program structure for establishing
connection-oriented client-server environment.
 */

/* server program */

#include &ltstdio.h>
#include &lterrno.h>
#include &ltsignal.h>
#include &ltsys/types.h>

#include &ltsys/socket.h>

struct sockaddr myname;
char buf[80];

main()
{
  int sock, new_sd, adrlen, cnt;

sock = socket(AF_UNIX, SOCK_STREAM, 0);
  if (sock < 0) {
printf("server socket failure %d\n", errno);
    perror("server: ");
    exit(1);
  }

  myname.sa_family = AF_UNIX;
  strcpy(myname.sa_data, "/tmp/billb");
  adrlen = strlen(myname.sa_data) +
      sizeof(myname.sa_family);

unlink("/tmp/billb"); /* defensive programming */
  if (bind(sock, &myname, adrlen) < 0) {
    printf("server bind failure %d\n", errno);
    perror("server: ");
    exit(1);
  }

  if (listen(sock, 5) < 0 {
  printf("server listen failure %d\n", errno);
    perror("server: ");
    exit(1);
  }

  /* Ignore child process termination.   */

  signal (SIGCHLD, SIG_IGN);

/*  Place the server in an infinite loop, waiting
  on connection requests to come from clients.
  In practice, there would need to be a clean
  way to terminate this process, but for now it
 will simply stay resident until terminated by
 the starting terminal or the super-user.    */

  while (1) {
if (new_sd = accept(sock,
 &myname, &adrlen)) < 0 {
 printf("server accept failure %d\n", errno);
      perror("server: ");
      exit(1);
    }

 /* Create child server process.  Parent does no
further processing -- it loops back to wait
  for another connection request.            */

printf("Socket address in server %d is %x, %s\n",
      getpid(), myname.sa_data, myname.sa_data);

    if (fork() == 0) {  /* child process */
    close (sock);  /* child does not need it  */
      /*  . . . . .  */

      cnt = read(new_sd, buf, strlen(buf));
   printf ("Server with pid %d got message %s\n",
         getpid(), buf);
      strcpy (buf, "Message to client");
      cnt = write(new_sd, buf, strlen(buf));
 printf("Socket address in server %d is %x, %s\n",
        getpid(), myname.sa_data, myname.sa_data);

      /*  . . . . .  */
    close (new_sd); /* close prior to exiting  */
      exit(0);
  }   /* closing bracket for if (fork() ... )  */

  }  /* closing bracket for while (1) ... ) */

}  /* closing bracket for main procedure */

/* client program */

#include &ltstdio.h>

#include &lterrno.h>
#include &ltsys/types.h>
#include &ltsys/socket.h>

char buf[80];
struct sockaddr myname;

main()
{
  int   sock, adrlen, cnt;

  sock = socket(AF_UNIX, SOCK_STREAM, 0);
  if (sock < 0) {
 printf("client socket failure %d\n", errno);
    perror("client: ");
    exit(1);
  }

  myname.sa_family = AF_UNIX;
  strcpy(myname.sa_data, "/tmp/billb");
  adrlen = strlen(myname.sa_data) +
      sizeof(myname.sa_family);

if (connect( sock, &myname, adrlen) < 0) {
    printf("client connect failure %d\n", errno);
    perror("client: ");
    exit(1);
  }
  /*  . . . . .  */

  strcpy(buf, "Message sent to server");
  cnt = write(sock, buf, strlen(buf));
  cnt = read(sock, buf, strlen(buf));
  printf("Client with pid %d got message %s\n",
     getpid(), buf);
printf("Socket address in server %d is %x, %s\n",
     getpid(), myname.sa_data, myname.sa_data);

  /*  . . . . .  */
  exit(0);
}

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