share/doc/psd/20.ipctut/socketpair.c

   1 .\"     $NetBSD: socketpair.c,v 1.2 1998/01/09 06:55:02 perry Exp $
   2 .\"
   3 .\" Copyright (c) 1986, 1993
   4 .\"     The Regents of the University of California.  All rights reserved.
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  30 .\"     @(#)socketpair.c        8.1 (Berkeley) 6/8/93
  31 .\"
  32 #include <sys/types.h>
  33 #include <sys/socket.h>
  34 #include <stdio.h>
  35
  36 #define DATA1 "In Xanadu, did Kublai Khan . . ."
  37 #define DATA2 "A stately pleasure dome decree . . ."
  38
  39 /*
  40  * This program creates a pair of connected sockets then forks and
  41  * communicates over them.  This is very similar to communication with pipes,
  42  * however, socketpairs are two-way communications objects. Therefore I can
  43  * send messages in both directions.
  44  */
  45
  46 main()
  47 {
  48         int sockets[2], child;
  49         char buf[1024];
  50
  51         if (socketpair(AF_UNIX, SOCK_STREAM, 0, sockets) < 0) {
  52                 perror("opening stream socket pair");
  53                 exit(1);
  54         }
  55
  56         if ((child = fork()) == -1)
  57                 perror("fork");
  58         else if (child) {       /* This is the parent. */
  59                 close(sockets[0]);
  60                 if (read(sockets[1], buf, 1024, 0) < 0)
  61                         perror("reading stream message");
  62                 printf("-->%s\en", buf);
  63                 if (write(sockets[1], DATA2, sizeof(DATA2)) < 0)
  64                         perror("writing stream message");
  65                 close(sockets[1]);
  66         } else {                /* This is the child. */
  67                 close(sockets[1]);
  68                 if (write(sockets[0], DATA1, sizeof(DATA1)) < 0)
  69                         perror("writing stream message");
  70                 if (read(sockets[0], buf, 1024, 0) < 0)
  71                         perror("reading stream message");
  72                 printf("-->%s\en", buf);
  73                 close(sockets[0]);
  74         }
  75 }