client.java

import java.io.IOException;
import java.net.*;
/*
Name: HENG WEILIANG
Group: SEP1
IP Address: 172.21.151.230
*/
public class Rfc865UdpClient {
    public static void main(String[] args) {
        // create datagram socket
        DatagramSocket socket = null;
        // define buffer length
        // as define in rfc865, message cannot be longer than 512 char
        int byteLength = 512;

        try {
            socket = new DatagramSocket();
        } catch (SocketException e) {
            System.out.println(e.getMessage());
        }

		try {
                        // define send message and convert to byte
			String sendMsg = "HENG WEILIANG, SEP1, 172.21.151.230";
			byte[] sendMsgByte = new byte[byteLength];
			sendMsgByte = sendMsg.getBytes();

                        // define ip address and port for server 
                        // server address 172.21.144.120
			InetAddress serverAddress = InetAddress.getByName("hw1-a00");

			int serverPort = 17;
                        
                        // create packet to be send
			DatagramPacket request = new DatagramPacket(sendMsgByte, sendMsgByte.length, serverAddress, serverPort);
                        // send packet
			socket.send(request);

                        // define buffer to receive reply message
			byte[] receiveMsgByte = new byte[byteLength];
                        // create packet object to receive reply message
			DatagramPacket reply = new DatagramPacket(receiveMsgByte, receiveMsgByte.length);

                        // try to receive reply
			try {

				socket.receive(reply);
			} catch (IOException ioEX) {
				System.out.println(ioEX.getMessage());

			}
                        // convert reply buffer to string
			String replyMsg = new String(receiveMsgByte);

			System.out.println(replyMsg);
                        
                        // close socket and connection
			socket.close();

		} catch (UnknownHostException hostEx) {
			System.out.println(hostEx.getMessage());
		} catch (IOException ioEX) {
			System.out.println(ioEX.getMessage());
		}
	}
}