Notes

import java.awt.*;
import java.net.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import java.io.*;


public class ServerInJava extends JFrame{
public JButton sendButton;
public JTextArea rxArea;
public JTextField txArea;
public JScrollPane pane;
public Container container;

public ServerInJava(String title)
{
super(title);

container = getContentPane();
container.setLayout(new FlowLayout());

txArea = new JTextField(50);
rxArea = new JTextArea(6,40);
rxArea.setEditable(false);
pane = new JScrollPane(rxArea);

sendButton = new JButton("Send");
sendButton.setEnabled(false);

container.add(pane);
container.add(txArea);
container.add(sendButton);

}
}

class UDPServerJava extends ServerInJava
{
InetAddress ip = null;
static int port;

public ButtonHandler bHandler;
DatagramSocket socket;

public UDPServerJava (String title)throws IOException
{
super(title);
bHandler = new ButtonHandler();
sendButton.addActionListener(bHandler);

socket = new DatagramSocket(5678);
}

private class ButtonHandler implements ActionListener
{
public void actionPerformed(ActionEvent e) {
tx();

}

}

public void tx()
{
try
{
byte[] buf = new byte[256];

String outputLine = txArea.getText();
buf = outputLine.getBytes();

rxArea.setText(rxArea.getText()+ "J>"+outputLine+"n");

DatagramPacket packet = new DatagramPacket(buf, buf.length,ip,port);
socket.send(packet);
}
catch(IOException e) {}
}


public void rx() throws IOException
{
DatagramPacket packet;
byte[] buf = new byte[256];

while(true)
{
packet = new DatagramPacket(buf, buf.length);
socket.receive(packet);

ip = packet.getAddress();
port = packet.getPort();

sendButton.setEnabled(true);

String received = new String(packet.getData());
rxArea.setText(rxArea.getText()+"A>" + received + "n");

}
}

public static void main (String[] args)throws IOException
{
UDPServerJava f = new UDPServerJava("Chat UDPServer Session");

f.pack();
f.setSize(500, 200);
f.setVisible(true);
f.rx();
}

}