dgramsend.c

.\" Copyright (c) 1986, 1993
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#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.
	 * Gethostbyname() 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\en", 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);
}