4.3BSD-Reno/share/doc/ps1/07.ipctut/dgramread.c

/*
 * Copyright (c) 1986 The Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#ifndef lint
char copyright[] =
"@(#) Copyright (c) 1986 The Regents of the University of California.\n\
 All rights reserved.\n";
#endif /* not lint */

#ifndef lint
static char sccsid[] = "@(#)dgramread.c	6.4 (Berkeley) 3/7/89";
#endif /* not lint */

#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);
}