以前学习过java，但是一直没接触到网络编程这一块，现在要把这一个知识盲点扫除掉

import java.awt.*;
import java.net.*;
import java.awt.event.*;
public class Chat extends Frame {

List lst = new List(6);
TextField tfIP = new TextField(15);
TextField tfData = new TextField(20);
//发送端
DatagramSocket ds = null;

public Chat(){
  try {
   ds = new DatagramSocket(3000);   
  }catch (Exception e) {
   e.printStackTrace();
  }
  
  this.add(lst,"Center");
  
  Panel p = new Panel();
  this.add(p,"South");
  p.setLayout(new BorderLayout());
  p.add(tfIP,"West");
  p.add(tfData,"East");
  
  //接收线程
  new Thread(new Runnable(){
   public void run(){
    byte[] buf = new byte[1024];
    DatagramPacket dp = new DatagramPacket(buf,buf.length);
    while(true){
     try{
      ds.receive(dp);
      //最新消息放首行
      lst.add(new String(buf,0,dp.getLength())
       +"    "+dp.getAddress().getHostAddress()+":"+dp.getPort()
       ,0);
     }catch(Exception e){
      //当Socket结束了，接收方法会出现异常
      if(!ds.isClosed()){
       System.out.print("接收端");
       e.printStackTrace();
      }
     }
    }
   
   }
  }).start();
  
  tfData.addActionListener(new ActionListener(){
   public void actionPerformed(ActionEvent e){
    //获取消息和IP
    byte[] buf = tfData.getText().getBytes();
    try{
     DatagramPacket dp = new DatagramPacket(
     buf,buf.length,
     InetAddress.getByName(tfIP.getText()),
     3000);
     ds.send(dp);
    }catch(Exception e1){
     e1.printStackTrace();
    }
    tfData.setText("");
   }
  });
  
  
  this.addWindowListener(new WindowAdapter(){
   public void windowClosing(WindowEvent e){
   
    ds.close();//关闭Socket
    dispose();
    System.exit(0);
   }
  });
}
   
    public static void main(String[] args) {
     Chat chat = new Chat();
     chat.setTitle("聊天窗口");
     chat.setBounds(300,200,300,400);
     chat.setVisible(true);
     chat.setResizable(false);
    }
}

值得学习ing!