Java网络编程实现的简单聊天室

import java.awt.*;
import java.awt.event.*;
import java.io.IOException;
import java.net.*;
import org.apache.log4j.Logger;
/**
 * 简单聊天室
 * The class <code>Chat</code>
 *
 * @author tongbo
 * @version 1.0
 */
public class Chat extends Frame{
    /**
     * 
     */
    private static final long serialVersionUID = 3139498857930944585L;
    private static final Logger LOGGER = Logger.getLogger(Chat.class);
    //定义只显示六行，多出会出现滚动条
    List list = new List(6);
    //定义ip地址的长度最长为15位
    TextField tfIP = new TextField(15);
    //文本消息输入框
    TextField tfData = new TextField(20);
    DatagramSocket ds = null;
    public Chat(){
        try {
            ds = new DatagramSocket(3000);
        } catch (SocketException e) {
            LOGGER.debug(e);
        }
        
        this.add(list,"Center");
        Panel panel = new Panel();
        this.add(panel,"South");
        
        panel.setLayout(new BorderLayout());
        panel.add(tfIP,"West");
        panel.add(tfData,"East");
        
        new Thread(new Runnable() {
            
            @Override
            public void run() {
                byte[] buf = new byte[1024];
                DatagramPacket dp = new DatagramPacket(buf, buf.length);
                LOGGER.debug("thread start......");
                while(true){
                    try {
                        ds.receive(dp);
                        LOGGER.debug("---"+new String(/*dp.getData()*/buf,0,dp.getLength())+" from "+
                                dp.getAddress().getHostAddress()+":"+dp.getPort());
                        //将消息字符串放置到0位置，即最上边
                        list.add(new String(/*dp.getData()*/buf,0,dp.getLength())+" from "+
                                dp.getAddress().getHostAddress()+":"+dp.getPort(),0);
                    } catch (IOException e) {
                        if(!ds.isClosed()){
                            LOGGER.debug(e);
                        }
                    }
                }
            }
        }).start();
        
        tfData.addActionListener(new ActionListener() {
            
            @Override
            public void actionPerformed(ActionEvent e) {
                byte[] buf;
                buf = tfData.getText().getBytes();
                try{
                    LOGGER.debug("ip:"+tfIP.getText());
                    DatagramPacket dp = new DatagramPacket(buf, buf.length, 
                            InetAddress.getByName(tfIP.getText()),3000);
                    ds.send(dp);
                }catch (Exception e1) {
                    LOGGER.debug(e1);
                }
                tfData.setText("");
            }
        });
        addWindowListener(new WindowAdapter() {
            
            @Override
            public void windowClosing(WindowEvent e) {
                ds.close();
                dispose();
                System.exit(0);
            }
        });
    }
    /**
     * @param args
     */
    public static void main(String[] args) {
        LOGGER.debug("chat start.....");
        Chat mainFrame = new Chat();
        mainFrame.setSize(300,400);
        mainFrame.setTitle("chat room");
        mainFrame.setVisible(true);
        mainFrame.setResizable(false);
    }
}