application1.java~2~

程序或系统实现的功能：利用数据报设计一个简单的聊天程序.

package packetreceivedemo;

import javax.swing.UIManager;
import java.awt.*;
import java.net.*;
import java.io.*;
public class Application1 {
  boolean packFrame = false;

  //Construct the application
  public Application1() {
    Frame1 frame = new Frame1();
    //Validate frames that have preset sizes
    //Pack frames that have useful preferred size info, e.g. from their layout
    if (packFrame) {
      frame.pack();
    }
    else {
      frame.validate();
    }
    //Center the window
    Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
    Dimension frameSize = frame.getSize();
    if (frameSize.height > screenSize.height) {
      frameSize.height = screenSize.height;
    }
    if (frameSize.width > screenSize.width) {
      frameSize.width = screenSize.width;
    }
    frame.setLocation((screenSize.width - frameSize.width) / 2, (screenSize.height - frameSize.height) / 2);
    frame.setVisible(true);
  }
  //Main method
  public static void main(String[] args) {
    try
          {	System.out.println ("Binding to local port 2000");
         DatagramSocket socket = new DatagramSocket(2000);
         System.out.println ("Bound to local port " + socket.getLocalPort());
         DatagramPacket packet = new DatagramPacket(new byte[256], 256 );
         socket.receive(packet);//写入发送方的地址和端口
         System.out.println ("Packet received!");
   // Display packet information
      InetAddress remote_addr = packet.getAddress();
      System.out.println ("Sent by  : " + remote_addr.getHostAddress() );
      System.out.println ("Send from: " + packet.getPort());
      // Display packet contents, by reading from byte array
      ByteArrayInputStream bin = new ByteArrayInputStream (packet.getData());
       for (int i=0; i < packet.getLength(); i++)
        { int data = bin.read();
          if (data == -1)break;
          else
           System.out.print ( (char) data) ; }
          socket.close();	}
        catch (IOException ioe)
              {	System.err.println ("Error - " + ioe);  }
           }
   // new Application1();
}