4.3BSD-Reno/share/doc/ps1/07.ipctut/dgramsend.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[] = "@(#)dgramsend.c	6.3 (Berkeley) 3/7/89";
#endif /* not lint */

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>

#define DATA "The sea is calm tonight, the tide is full . . ."

/*
 * Here I send a datagram to a receiver whose name I get from the command
 * line arguments.  The form of the command line is dgramsend hostname
 * portnumber 
 */

main(argc, argv)
	int argc;
	char *argv[];
{
	int sock;
	struct sockaddr_in name;
	struct hostent *hp, *gethostbyname();

	/* Create socket on which to send. */
	sock = socket(AF_INET, SOCK_DGRAM, 0);
	if (sock < 0) {
		perror("opening datagram socket");
		exit(1);
	}
	/*
	 * Construct name, with no wildcards, of the socket to send to.
	 * Getnostbyname() returns a structure including the network address
	 * of the specified host.  The port number is taken from the command
	 * line. 
	 */
	hp = gethostbyname(argv[1]);
	if (hp == 0) {
		fprintf(stderr, "%s: unknown host\n", argv[1]);
		exit(2);
	}
	bcopy(hp->h_addr, &name.sin_addr, hp->h_length);
	name.sin_family = AF_INET;
	name.sin_port = htons(atoi(argv[2]));
	/* Send message. */
	if (sendto(sock, DATA, sizeof(DATA), 0, &name, sizeof(name)) < 0)
		perror("sending datagram message");
	close(sock);
}