例11-9.txt

Java大学实用教程 耿祥义编著 课件 PPT

Receive.java 
import java.net.*;
import java.awt.*; 
import java.awt.event.*;
import javax.swing.*;
public class Receive extends JFrame implements Runnable,ActionListener
{ 
    int port;                                        //组播的端口。 
    InetAddress group=null;                          //组播组的地址。
    MulticastSocket socket=null;                     //多点广播套接字。 
    JButton startReceive,stopReceive;   
    JTextArea showArea;  
    Thread thread;                                   //负责接收信息的线程。
    boolean stop=false;
    public Receive()
    { 
     super("定时接收信息");
     thread=new Thread(this);
     startReceive=new JButton("开始接收");
     stopReceive=new JButton("停止接收");
     startReceive.addActionListener(this); 
     stopReceive.addActionListener(this); 
     showArea=new JTextArea(10,10);
     JPanel north=new JPanel();
     north.add(startReceive);
     north.add(stopReceive);
     Container con=getContentPane();
     con.add(north,BorderLayout.NORTH);
     con.add(new JScrollPane(showArea),BorderLayout.CENTER);
     port=5858;                                     
     try
         {
             group=InetAddress.getByName("239.255.8.0"); 
             socket=new MulticastSocket(port);        
             socket.joinGroup(group);       
                                   
         }
     catch(Exception e){} 
     setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     setSize(320,300);
     validate();
     setVisible(true);   
  }
  public void actionPerformed(ActionEvent e)
  { 
      if(e.getSource()==startReceive)
      { 
        if(!(thread.isAlive()))
           {  
               thread=new Thread(this);
           }
        try{ 
               thread.start(); 
           }
        catch(Exception ee) {}
      }
    if(e.getSource()==stopReceive)
      { 
         stop=true; 
      }
   }
   public void run()
   { 
      while(true)   
      {
         byte data[]=new byte[8192];
         DatagramPacket packet=null;
         packet=new DatagramPacket(data,data.length,group,port); 
         try 
            { 
              socket.receive(packet);
              String message=new String(packet.getData(),0,packet.getLength());
              showArea.append("\n"+message);
              showArea.setCaretPosition(showArea.getText().length());
            }
        catch(Exception e) {}
        if(stop==true)
           {  
              break;
           } 
      } 
   }
   public static void main(String args[])
   { 
      new Receive();
   }
}