xref: /netbsd-src/share/doc/psd/20.ipctut/socketpair.c (revision 075022b349321510ad14036d70908681ed02f117)
1*075022b3Sagc .\"	$NetBSD: socketpair.c,v 1.3 2003/08/07 10:30:50 agc Exp $
26d400d56Sperry .\"
3d9158b13Scgd .\" Copyright (c) 1986, 1993
4d9158b13Scgd .\"	The Regents of the University of California.  All rights reserved.
5d9158b13Scgd .\"
6d9158b13Scgd .\" Redistribution and use in source and binary forms, with or without
7d9158b13Scgd .\" modification, are permitted provided that the following conditions
8d9158b13Scgd .\" are met:
9d9158b13Scgd .\" 1. Redistributions of source code must retain the above copyright
10d9158b13Scgd .\"    notice, this list of conditions and the following disclaimer.
11d9158b13Scgd .\" 2. Redistributions in binary form must reproduce the above copyright
12d9158b13Scgd .\"    notice, this list of conditions and the following disclaimer in the
13d9158b13Scgd .\"    documentation and/or other materials provided with the distribution.
14*075022b3Sagc .\" 3. Neither the name of the University nor the names of its contributors
15d9158b13Scgd .\"    may be used to endorse or promote products derived from this software
16d9158b13Scgd .\"    without specific prior written permission.
17d9158b13Scgd .\"
18d9158b13Scgd .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
19d9158b13Scgd .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20d9158b13Scgd .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21d9158b13Scgd .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
22d9158b13Scgd .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23d9158b13Scgd .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24d9158b13Scgd .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25d9158b13Scgd .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26d9158b13Scgd .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27d9158b13Scgd .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28d9158b13Scgd .\" SUCH DAMAGE.
29d9158b13Scgd .\"
30d9158b13Scgd .\"	@(#)socketpair.c	8.1 (Berkeley) 6/8/93
31d9158b13Scgd .\"
32d9158b13Scgd #include <sys/types.h>
33d9158b13Scgd #include <sys/socket.h>
34d9158b13Scgd #include <stdio.h>
35d9158b13Scgd 
36d9158b13Scgd #define DATA1 "In Xanadu, did Kublai Khan . . ."
37d9158b13Scgd #define DATA2 "A stately pleasure dome decree . . ."
38d9158b13Scgd 
39d9158b13Scgd /*
40d9158b13Scgd  * This program creates a pair of connected sockets then forks and
41d9158b13Scgd  * communicates over them.  This is very similar to communication with pipes,
42d9158b13Scgd  * however, socketpairs are two-way communications objects. Therefore I can
43d9158b13Scgd  * send messages in both directions.
44d9158b13Scgd  */
45d9158b13Scgd 
46d9158b13Scgd main()
47d9158b13Scgd {
48d9158b13Scgd 	int sockets[2], child;
49d9158b13Scgd 	char buf[1024];
50d9158b13Scgd 
51d9158b13Scgd 	if (socketpair(AF_UNIX, SOCK_STREAM, 0, sockets) < 0) {
52d9158b13Scgd 		perror("opening stream socket pair");
53d9158b13Scgd 		exit(1);
54d9158b13Scgd 	}
55d9158b13Scgd 
56d9158b13Scgd 	if ((child = fork()) == -1)
57d9158b13Scgd 		perror("fork");
58d9158b13Scgd 	else if (child) {	/* This is the parent. */
59d9158b13Scgd 		close(sockets[0]);
60d9158b13Scgd 		if (read(sockets[1], buf, 1024, 0) < 0)
61d9158b13Scgd 			perror("reading stream message");
62d9158b13Scgd 		printf("-->%s\en", buf);
63d9158b13Scgd 		if (write(sockets[1], DATA2, sizeof(DATA2)) < 0)
64d9158b13Scgd 			perror("writing stream message");
65d9158b13Scgd 		close(sockets[1]);
66d9158b13Scgd 	} else {		/* This is the child. */
67d9158b13Scgd 		close(sockets[1]);
68d9158b13Scgd 		if (write(sockets[0], DATA1, sizeof(DATA1)) < 0)
69d9158b13Scgd 			perror("writing stream message");
70d9158b13Scgd 		if (read(sockets[0], buf, 1024, 0) < 0)
71d9158b13Scgd 			perror("reading stream message");
72d9158b13Scgd 		printf("-->%s\en", buf);
73d9158b13Scgd 		close(sockets[0]);
74d9158b13Scgd 	}
75d9158b13Scgd }
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