BSD 4_3_Net_2 release

[unix-history] / usr / src / share / doc / ps1 / 07.ipctut / dgramread.c

.\" Copyright (c) 1986 The Regents of the University of California.
.\" All rights reserved.
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.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
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.\"    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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.\"	@(#)dgramread.c	6.4 (Berkeley) 4/17/91
.\"
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <stdio.h>

/*
 * In the included file <netinet/in.h> a sockaddr_in is defined as follows:
 * struct sockaddr_in {
 *	short	sin_family;
 *	u_short	sin_port;
 *	struct in_addr sin_addr;
 *	char	sin_zero[8];
 * }; 
 *
 * This program creates a datagram socket, binds a name to it, then reads
 * from the socket.
 */
main()
{
	int sock, length;
	struct sockaddr_in name;
	char buf[1024];

	/* Create socket from which to read. */
	sock = socket(AF_INET, SOCK_DGRAM, 0);
	if (sock < 0) {
		perror("opening datagram socket");
		exit(1);
	}
	/* Create name with wildcards. */
	name.sin_family = AF_INET;
	name.sin_addr.s_addr = INADDR_ANY;
	name.sin_port = 0;
	if (bind(sock, &name, sizeof(name))) {
		perror("binding datagram socket");
		exit(1);
	}
	/* Find assigned port value and print it out. */
	length = sizeof(name);
	if (getsockname(sock, &name, &length)) {
		perror("getting socket name");
		exit(1);
	}
	printf("Socket has port #%d\en", ntohs(name.sin_port));
	/* Read from the socket */
	if (read(sock, buf, 1024) < 0)
		perror("receiving datagram packet");
	printf("-->%s\en", buf);
	close(sock);
}