UDPClient

import java.io.*;
import java.net.*;

public class UDPClient
{
    private GUIForClient gfc;

    public UDPClient(GUIForClient gfc)
    {
        this.gfc = gfc;
    }

    public static void main(String[] args) throws Exception
    {
        int cport = 29841;
        String host = "localhost";

        if (args.length < 1)
        {
            System.out.println("You are now connected to the host: " + host + " On port number: " + cport);
        }
        else{
            cport = Integer.valueOf(args[0]).intValue();
            System.out.println("You are now connected to the host: " + host + " On port number: " + cport);
        }

        InetAddress ia = InetAddress.getByName(host);
        SendThread send = new SendThread(ia, cport);
        send.start();
        ReceiveThread receive = new ReceiveThread(send.getSocket());
        receive.start();
    }

}

class SendThread extends Thread
{
    private InetAddress serverIP;
    private DatagramSocket ds;
    private boolean stopThread = false;
    private int sport;

    public SendThread(InetAddress addr, int sport) throws SocketException
    {
        this.serverIP = addr;
        this.sport = sport;
        this.ds = new DatagramSocket();
        this.ds.connect(serverIP, sport);
    }

    public void halt()
    {
        this.stopThread = true;
    }

    public DatagramSocket getSocket()
    {
        return this.ds;
    }

    public void run()
    {
        try
        {
            byte[] b1 = new byte[1024];
            b1 = "".getBytes();
            DatagramPacket dp1 = new DatagramPacket(b1, b1.length, serverIP, sport);
            ds.send(dp1);

            BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

            while (true)
            {
                if (stopThread)
                {
                    return;
                }

                String messageFromClient = br.readLine();

                if (messageFromClient.equals("."))
                {
                    break;
                }

                byte[] sentData = new byte[1024];

                sentData = messageFromClient.getBytes();

                DatagramPacket dp2 = new DatagramPacket(sentData, sentData.length, serverIP, sport);

                System.out.println("Please type your next message.");

                ds.send(dp2);

                Thread.yield();
            }
        }
        catch(IOException ioe)
        {
            System.err.println(ioe);
        }
    }
}

class ReceiveThread extends Thread
{
    private DatagramSocket ds;
    private boolean stopThread = false;

    public ReceiveThread(DatagramSocket ds) throws SocketException
    {
        this.ds = ds;
    }

    private void halt()
    {
        this.stopThread = true;
    }

    public void run()
    {
        byte[] receivedData = new byte[1024];

        while (true)
        {
            if(stopThread)
            {
                return;
            }

            DatagramPacket dp3 = new DatagramPacket(receivedData, receivedData.length);
            System.out.println("You're in the client!");
            try
            {
                ds.receive(dp3);
                System.out.println("I will keep receiving packets...");

                String replyFromServer = new String(dp3.getData(), 0, dp3.getLength());

                System.out.println("UDPClient: Response from the server: \"" + replyFromServer + "\"\n");

                Thread.yield();
            }
            catch(IOException ioe)
            {
                System.err.println(ioe);
            }
        }
    }
}