time_client.c

/* time_client.c - main */

#include <sys/types.h>

#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <sys/socket.h>                                                                            
#include <netinet/in.h>
#include <arpa/inet.h>
                                                                                
#include <netdb.h>

#define	BUFSIZE 64

#define	MSG		"Any Message \n"


/*------------------------------------------------------------------------
 * main - UDP client for TIME service that prints the resulting time
 *------------------------------------------------------------------------
 */
int
main(int argc, char **argv)
{
	char	*host = "localhost";
	int	port = 3000;
	char	now[100];		/* 32-bit integer to hold time	*/ 
	struct hostent	*phe;	/* pointer to host information entry	*/
	struct sockaddr_in sin;	/* an Internet endpoint address		*/
	int	s, n, type;	/* socket descriptor and socket type	*/

	switch (argc) {
	case 1:
		break;
	case 2:
		host = argv[1];
	case 3:
		host = argv[1];
		port = atoi(argv[2]);
		break;
	default:
		fprintf(stderr, "usage: UDPtime [host [port]]\n");
		exit(1);
	}

	memset(&sin, 0, sizeof(sin));
        sin.sin_family = AF_INET;                                                                
        sin.sin_port = htons(port);
                                                                                        
    /* Map host name to IP address, allowing for dotted decimal */
        if ( phe = gethostbyname(host) ){
                memcpy(&sin.sin_addr, phe->h_addr, phe->h_length);
        }
        else if ( (sin.sin_addr.s_addr = inet_addr(host)) == INADDR_NONE )
		fprintf(stderr, "Can't get host entry \n");
                                                                                
    /* Allocate a socket */
        s = socket(AF_INET, SOCK_DGRAM, 0);
        if (s < 0)
		fprintf(stderr, "Can't create socket \n");
	
                                                                                
    /* Connect the socket */
        if (connect(s, (struct sockaddr *)&sin, sizeof(sin)) < 0)
		fprintf(stderr, "Can't connect to %s %s \n", host, "Time");


	(void) write(s, MSG, strlen(MSG));

	/* Read the time */

	n = read(s, (char *)&now, sizeof(now));
	if (n < 0)
		fprintf(stderr, "Read failed\n");
	write(1, now, n);
	exit(0);
}