if (argc != 4)
err_quit("usage: udpcli <IPaddress> <his-Port> <mine-Port>\n");
sockfd = Socket(AF_INET, SOCK_DGRAM, 0);
 
memset( &servaddr, 0, sizeof(servaddr) );
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
servaddr.sin_port = htons(atoi( argv[3]) );
//servaddr.sin_port = htons( SERVER_PORT );
Bind(sockfd, (struct sockaddr *) &servaddr, sizeof(servaddr) );
 
printf("Peer-Server initiated...listening in %s  and port %d\n\t waiting for clients\n",
		argv[1], ntohs(servaddr.sin_port));

memset( &hisaddr, 0, sizeof(hisaddr) );
	hisaddr.sin_family = AF_INET;
	hisaddr.sin_port = htons( atoi(argv[3]) );
	Inet_pton( AF_INET, argv[1], &hisaddr.sin_addr);

	if((childpid = fork()) == 0)
	{
		//send message to peer
		peer_dg_send(stdin, sockfd, (struct sockaddr *) &hisaddr, sizeof(hisaddr));
	}
	else
	{
		//receive message from peer
		peer_dg_receive(sockfd, (struct sockaddr *)  &hisaddr, sizeof(hisaddr) ); 
 
	}

void peer_dg_receive(int sockfd, struct sockaddr * pcliaddr, socklen_t clilen)
{
	int n;
	socklen_t len;
	char mesg[MAXLINE];
 
	for(;;)
	{
		len = clilen;
		n = Recvfrom(sockfd, mesg, MAXLINE, 0, pcliaddr, &len);
 
		mesg[n] = 0;	/* null terminate */
		//Fputs(mesg, stdout);
		printf("Received: %s", mesg);
	}
}
 
void peer_dg_send(FILE *fp, int sockfd, struct sockaddr *pservaddr, socklen_t servlen)
{
	int	n;
	char	sendline[MAXLINE];
 
	while (Fgets(sendline, MAXLINE, fp) != NULL) 
	{
		Sendto(sockfd, sendline, strlen(sendline), 0, pservaddr, servlen);
	}
 
}