import java.awt.Button;
import java.awt.Frame;
import java.awt.TextArea;
import java.awt.TextField;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;


class PC100 extends Frame implements Runnable,ActionListener{
    TextField out=new TextField("send to pc2");
    TextArea in=new TextArea();
    Button b=new Button("send");
    
    PC100(){
        super("This is pc1");
        setSize(200,200);
        setVisible(true);
        b.addActionListener(this);
        add(out,"South");
        add(in,"Center");
        add(b,"North");
        Thread t=new Thread(this);
        t.start();
        
        this.addWindowListener(new WindowAdapter(){
            public void windowClosing(WindowEvent e){
                System.exit(0);
            }
        });
    }
    
    @Override
    public void run() {
        // TODO Auto-generated method stub
        
        DatagramPacket pack=null;
        DatagramSocket mail=null;
        byte data[]=new byte[8192];
        try{
            pack=new DatagramPacket(data,data.length);
            mail=new DatagramSocket(9998);////////////////////////
        }catch(Exception e){
            e.printStackTrace();
            System.out.println("run01 error!");
            }
        while(true){
            if(mail==null)
                break;
            else
                try{
                    mail.receive(pack);   //////////异常。。。。。
                    int length=pack.getLength();
                    InetAddress add=pack.getAddress();
                    int port=pack.getPort();
                    String msg=new String(pack.getData(),0,length);
                    in.append("length:"+length+"\n");
                    in.append("From:"+add+"port:"+port+"\n");
                    in.append("data:"+msg+"\n");
                }catch(Exception e){
                    e.printStackTrace();
                    in.append("run22\n");break;
                    }
        }
    }

    @Override
    public void actionPerformed(ActionEvent event) {
        // TODO Auto-generated method stub
        
        byte buffer[]=out.getText().trim().getBytes();
        try{
            InetAddress add=InetAddress.getByName("127.0.0.1");
            //////////////////////
            DatagramPacket data=new DatagramPacket(buffer,buffer.length,add,9998);
            DatagramSocket mail=new DatagramSocket();
            in.append("IP:"+data.getAddress()+"\n");
            in.append("port:"+data.getPort()+"\n");
            in.append("length:"+data.getLength()+"\n");
            mail.send(data);
        }catch(Exception e){System.out.println("send error!");}
        
    }
}

public class PC1{
    public static void main(String args[]){
        PC100 pc10=new PC100();
        pc10.validate();
    }
}

java.net.SocketException: Socket closed
    at java.net.PlainDatagramSocketImpl.receive0(Native Method)
    at java.net.PlainDatagramSocketImpl.receive(PlainDatagramSocketImpl.java:136)
    at java.net.DatagramSocket.receive(DatagramSocket.java:712)
    at PC100.run(PC1.java:56)
    at java.lang.Thread.run(Thread.java:619)