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socketpair.c revision 1.1 
      1 .\" Copyright (c) 1986, 1993
      2 .\"	The Regents of the University of California.  All rights reserved.
      3 .\"
      4 .\" Redistribution and use in source and binary forms, with or without
      5 .\" modification, are permitted provided that the following conditions
      6 .\" are met:
      7 .\" 1. Redistributions of source code must retain the above copyright
      8 .\"    notice, this list of conditions and the following disclaimer.
      9 .\" 2. Redistributions in binary form must reproduce the above copyright
     10 .\"    notice, this list of conditions and the following disclaimer in the
     11 .\"    documentation and/or other materials provided with the distribution.
     12 .\" 3. All advertising materials mentioning features or use of this software
     13 .\"    must display the following acknowledgement:
     14 .\"	This product includes software developed by the University of
     15 .\"	California, Berkeley and its contributors.
     16 .\" 4. Neither the name of the University nor the names of its contributors
     17 .\"    may be used to endorse or promote products derived from this software
     18 .\"    without specific prior written permission.
     19 .\"
     20 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     21 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     22 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     23 .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     24 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     25 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     26 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     27 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     28 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     29 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     30 .\" SUCH DAMAGE.
     31 .\"
     32 .\"	@(#)socketpair.c	8.1 (Berkeley) 6/8/93
     33 .\"
     34 #include <sys/types.h>
     35 #include <sys/socket.h>
     36 #include <stdio.h>
     37 
     38 #define DATA1 "In Xanadu, did Kublai Khan . . ."
     39 #define DATA2 "A stately pleasure dome decree . . ."
     40 
     41 /*
     42  * This program creates a pair of connected sockets then forks and
     43  * communicates over them.  This is very similar to communication with pipes,
     44  * however, socketpairs are two-way communications objects. Therefore I can
     45  * send messages in both directions.
     46  */
     47 
     48 main()
     49 {
     50 	int sockets[2], child;
     51 	char buf[1024];
     52 
     53 	if (socketpair(AF_UNIX, SOCK_STREAM, 0, sockets) < 0) {
     54 		perror("opening stream socket pair");
     55 		exit(1);
     56 	}
     57 
     58 	if ((child = fork()) == -1)
     59 		perror("fork");
     60 	else if (child) {	/* This is the parent. */
     61 		close(sockets[0]);
     62 		if (read(sockets[1], buf, 1024, 0) < 0)
     63 			perror("reading stream message");
     64 		printf("-->%s\en", buf);
     65 		if (write(sockets[1], DATA2, sizeof(DATA2)) < 0)
     66 			perror("writing stream message");
     67 		close(sockets[1]);
     68 	} else {		/* This is the child. */
     69 		close(sockets[1]);
     70 		if (write(sockets[0], DATA1, sizeof(DATA1)) < 0)
     71 			perror("writing stream message");
     72 		if (read(sockets[0], buf, 1024, 0) < 0)
     73 			perror("reading stream message");
     74 		printf("-->%s\en", buf);
     75 		close(sockets[0]);
     76 	}
     77 }
     78