/* A simple echo client using TCP from Leon-Garcia and Widjaja's book
   "Communication Networks: Fundamental Concepts and Key Architectures,"
	 McGraw-Hill, 2000, pages 72 - 74.
*/

#include <stdio.h>
#include <netdb.h>																/* for gethostbyname() */
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

#define SERVER_TCP_PORT		3000	/* well known port */
#define	BUFLEN						 256	/* buffer length */

int main (int argc, char **argv)
{
	int			n, bytes_to_read;
	int			sd,	port;
	struct	hostent *hp;
	struct	sockaddr_in	server;
	char		*host, *bp, rbuf[BUFLEN], sbuf[BUFLEN];
	
	switch(argc) {
	case 2:
		host = argv[1];
		port = SERVER_TCP_PORT;
		break;
	case 3:
		host = argv[1];
		port = atoi(argv[2]);
		break;
	default:
		fprintf(stderr, "Usage: %s host [port]\n", argv[0]);
		exit(1);
	}

	/* Create a stream socket (TCP, connection-oriented) */
	if ((sd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
		fprintf(stderr, "%s: Can't create a socket.\n", argv[0]);
		exit(1);
	}

	/* Bind an address to the socket */
	bzero((char *)&server, sizeof(struct sockaddr_in));
	server.sin_family 			= AF_INET;							/* Internet connection */
	server.sin_port   			= htons(port);					/* Define the port #   */
	if ((hp = gethostbyname(host)) == NULL) {
		fprintf(stderr, "%s: Can't get server's address.\n", argv[0]);
		exit(1);
	}
	bcopy(hp->h_addr, (char *)&server.sin_addr, hp->h_length);

	/* Connecting to the server */
	if (connect(sd, (struct sockaddr *)&server, sizeof(server)) == -1) {
		fprintf(stderr, "%s: Can't connect to server.\n", argv[0]);
		exit(1);
	}
	printf("%s: Connected to server %s.\n", argv[0], hp->h_name);
	printf("%s: String to transmit? ", argv[0]);		/* Prompt user for a string */
	gets(sbuf);																			/* Read user input string */
	write(sd, sbuf, BUFLEN);												/* Send string to echo server */

	printf("%s: String received = ", argv[0]);
	bp = rbuf;
	bytes_to_read = BUFLEN;
	while ((n = read(sd, bp, bytes_to_read)) > 0) {
		bp += n;
		bytes_to_read -= n;
	}
	printf("%s\n", rbuf);

	close(sd);	
	return(0);
}