/* A simple echo server 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 <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,	new_sd, client_len, port;
	struct	sockaddr_in	server, client;
	char		*bp, buf[BUFLEN];
	
	switch(argc) {
	case 1:
		port = SERVER_TCP_PORT;
		break;
	case 2:
		port = atoi(argv[1]);
		break;
	default:
		fprintf(stderr, "Usage: %s [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 #   */
	server.sin_addr.s_addr 	= htonl(INADDR_ANY);		/* Use any server address */
	if (bind(sd, (struct sockaddr *)&server, sizeof(server)) == -1) {
		fprintf(stderr, "%s: Can't bind name to socket.\n", argv[0]);
		exit(1);
	}

	/* Queue upt to five connect requests */
	listen(sd, 5);

	while(1) {
		client_len = sizeof(client);
		if ((new_sd = accept(sd, (struct sockaddr *)&client, &client_len)) == -1) {
			fprintf(stderr, "%s: Can't accept client.\n", argv[0]);
			exit(1);
		}

		bp = buf;
		bytes_to_read = BUFLEN;	
		while ((n = read(new_sd, bp, bytes_to_read)) > 0) {
			bp += n;
			bytes_to_read -= n;
		}

		printf("Received string = %s\n", buf);
		write(new_sd, buf, BUFLEN);			/* echo the message */
		close(new_sd);
	}

	close(sd);			/* This statement is inaccessible! */
	return(0);
}