/* Echo server using UDP */
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

#define SERVER_UDP_PORT		5000	
#define MAXLEN		4096

int main(int argc, char **argv)
{
	int 	sd, client_len, port, n;
	char 	buf[MAXLEN];
	struct 	sockaddr_in 	server, client;

	switch(argc) {
	case 1:
		port = SERVER_UDP_PORT;
		break;
	case 2:
		port = atoi(argv[1]);
		break;
	default:
		fprintf(stderr, "Usage: %s [port]\n", argv[0]);
		exit(1);
	}
		
	/* Create a datagram socket */
	if ((sd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
		fprintf(stderr, "Can't create a socket\n");
		exit(1);
	}


	/* Bind an address to the socket */
	bzero((char *)&server, sizeof(server));
	server.sin_family = AF_INET;
	server.sin_port = htons(port);
	server.sin_addr.s_addr = htonl(INADDR_ANY);
	if (bind(sd, (struct sockaddr *)&server, 
	sizeof(server)) == -1) {
		fprintf(stderr, "Can't bind name to socket\n");
		exit(1);
	}

	while (1) {
		client_len = sizeof(client);
		if ((n = recvfrom(sd, buf, MAXLEN, 0, 
		(struct sockaddr *)&client, &client_len)) < 0) {
		      fprintf(stderr, "Can't receive datagram\n");
		      exit(1);
		}

		if (sendto(sd, buf, n, 0, 
		(struct sockaddr *)&client, client_len) != n) {
		      fprintf(stderr, "Can't send datagram\n");
		      exit(1);
		}
	}
	close(sd);
	return(0);
}