/* This file is part of the sample code and exercises
 * used by the class "Advanced Programming in the UNIX
 * Environment" taught by Jan Schaumann
 * <jschauma@netmeister.org> at Stevens Institute of
 * Technology.
 *
 * https://stevens.netmeister.org/631/
 */

/*	$NetBSD: dgramread.c,v 1.3 2003/08/07 10:30:50 agc Exp $
 *
 * 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. 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.
 *
 * 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
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)dgramread.c	8.1 (Berkeley) 6/8/93
 */
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.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.
 */
int main()
{
	int sock;
	socklen_t length;
	struct sockaddr_in name;
	char buf[BUFSIZ];

	memset(&name, 0, sizeof(name));

	if ((sock = socket(PF_INET, SOCK_DGRAM, 0)) < 0) {
		perror("opening datagram socket");
		exit(EXIT_FAILURE);
	}

	name.sin_family = PF_INET;
	name.sin_addr.s_addr = INADDR_ANY;
	name.sin_port = 0;
	if (bind(sock, (struct sockaddr *)&name, sizeof(name)) < 0) {
		perror("binding datagram socket");
		exit(EXIT_FAILURE);
	}

	/* Find assigned port value and print it out. */
	length = sizeof(name);
	if (getsockname(sock, (struct sockaddr *)&name, &length) < 0) {
		perror("getting socket name");
		exit(EXIT_FAILURE);
	}
	(void)printf("Socket has port #%d\n", ntohs(name.sin_port));
	if (read(sock, buf, BUFSIZ) < 0)
		perror("receiving datagram packet");
	(void)printf("-->%s\n", buf);
	(void)close(sock);
	return EXIT_SUCCESS;
}