.\" Copyright (c) 1986, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\"
.\"	@(#)socketpair.c	8.1 (Berkeley) 6/8/93
.\"
#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>

#define DATA1 "In Xanadu, did Kublai Khan . . ."
#define DATA2 "A stately pleasure dome decree . . ."

/*
 * This program creates a pair of connected sockets then forks and
 * communicates over them.  This is very similar to communication with pipes,
 * however, socketpairs are two-way communications objects. Therefore I can
 * send messages in both directions.
 */

main()
{
	int sockets[2], child;
	char buf[1024];

	if (socketpair(AF_UNIX, SOCK_STREAM, 0, sockets) < 0) {
		perror("opening stream socket pair");
		exit(1);
	}

	if ((child = fork()) == -1)
		perror("fork");
	else if (child) {	/* This is the parent. */
		close(sockets[0]);
		if (read(sockets[1], buf, 1024, 0) < 0)
			perror("reading stream message");
		printf("-->%s\en", buf);
		if (write(sockets[1], DATA2, sizeof(DATA2)) < 0)
			perror("writing stream message");
		close(sockets[1]);
	} else {		/* This is the child. */
		close(sockets[1]);
		if (write(sockets[0], DATA1, sizeof(DATA1)) < 0)
			perror("writing stream message");
		if (read(sockets[0], buf, 1024, 0) < 0)
			perror("reading stream message");
		printf("-->%s\en", buf);
		close(sockets[0]);
	}
}
