4.3BSD/usr/guest/karels/tests/udpconnect.c

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

main(argc, argv)
	char *argv[];
{
	struct sockaddr_in sin;
	struct hostent *hp;
	struct servent *sp;
	int s, buflen;
	char buf[BUFSIZ], *ntoa();

	if (argc < 3) {
		printf("usage: mesg service host\n");
		exit(1);
	}
	sp = getservbyname(argv[1], "udp");
	if (sp == NULL)   {
		printf("%s: no service\n", argv[1]);
		exit(1);
	}
	bzero(&sin, sizeof (sin));
	hp = gethostbyname(argv[2]);
	if (hp) {
		sin.sin_family = hp->h_addrtype;
		bcopy(hp->h_addr, &sin.sin_addr, hp->h_length);
	} else {
		sin.sin_family = AF_INET;
		sin.sin_addr.s_addr = inet_addr(argv[2]);
		if (sin.sin_addr.s_addr == -1) {
			printf("unknown host %s\n", argv[2]);
			return;
		}
	}

	sin.sin_port = sp->s_port;
	s = socket(SOCK_DGRAM, AF_INET, 0);
	if (s < 0) {
		perror("socket");
		exit(1);
	}
	if (connect(s, &sin, sizeof (sin)) < 0)
		perror("connect");
	printf("Test message?\n");
	fflush(stdout);
	if (fgets(buf, sizeof (buf), stdin) == NULL) {
		printf("No text?\n");
	}
	buflen = strlen(buf);
	printf("send %s.%d\n", ntoa(sin.sin_addr),
		(unsigned)ntohs(sin.sin_port));
	if (send(s, buf, buflen, 0) < 0)
		perror("send");
}

/*
 * Convert network-format internet address
 * to base 256 d.d.d.d representation.
 */
char *
ntoa(in)
	struct in_addr in;
{
	static char b[18];
	register char *p;

	p = (char *)&in;
#define	UC(b)	(((int)b)&0xff)
	sprintf(b, "%d.%d.%d.%d", UC(p[0]), UC(p[1]), UC(p[2]), UC(p[3]));
	return (b);
}