udpchat.java

打开两个以上的窗口来进行聊天, 即连续运行两次即可. Windows 下可以点击 编译.bat 和 运行.bat 来编译, 运行. 项目代码也可以导入 Eclipse 运行.

import java.awt.*;
import java.io.*;
import java.net.*;
import java.awt.event.*;

/**
 * The multicast datagram socket class is useful for sending
 * and receiving IP multicast packets.  A MulticastSocket is
 * a (UDP) DatagramSocket, with additional capabilities for
 * joining "groups" of other multicast hosts on the internet.
 * <P>
 * A multicast group is specified by a class D IP address, those
 * in the range <CODE>224.0.0.1</CODE> to <CODE>239.255.255.255</CODE>,
 * inclusive, and by a standard UDP port number.  One would join a
 * multicast group by first creating a MulticastSocket with the desired
 * port, then invoking the <CODE>joinGroup(InetAddress groupAddr)</CODE>
 * method:
 * <PRE>
 * // join a Multicast group and send the group salutations
 * ...
 * byte[] msg = {'H', 'e', 'l', 'l', 'o'};
 * InetAddress group = InetAddress.getByName("228.5.6.7");
 * MulticastSocket s = new MulticastSocket(6789);
 * s.joinGroup(group);
 * DatagramPacket hi = new DatagramPacket(msg, msg.length,
 *                             group, 6789);
 * s.send(hi);
 * // get their responses!
 * byte[] buf = new byte[1000];
 * DatagramPacket recv = new DatagramPacket(buf, buf.length);
 * s.receive(recv);
 * ...
 * // OK, I'm done talking - leave the group...
 * s.leaveGroup(group);
 * </PRE>
 *
 * When one sends a message to a multicast group, <B>all</B> subscribing
 * recipients to that host and port receive the message (within the
 * time-to-live range of the packet, see below).  The socket needn't
 * be a member of the multicast group to send messages to it.
 * <P>
 * When a socket subscribes to a multicast group/port, it receives
 * datagrams sent by other hosts to the group/port, as do all other
 * members of the group and port.  A socket relinquishes membership
 * in a group by the leaveGroup(InetAddress addr) method.  <B>
 * Multiple MulticastSocket's</B> may subscribe to a multicast group
 * and port concurrently, and they will all receive group datagrams.
 * <P>
 * Currently applets are not allowed to use multicast sockets.
 */

public class UDPChat extends Frame {
  InetAddress group = null;
  MulticastSocket socket = null;
  String username;
  int port;

  TextArea textArea = new TextArea();
  Panel configPanel = new Panel();
  Label ipLabel = new Label();
  TextField ipField = new TextField(10);
  Label portLabel = new Label();
  TextField portField = new TextField(10);
  Label nameLabel = new Label();
  TextField nameField = new TextField(10);
  Panel messagePanel = new Panel();
  Button joinButton = new Button();
  Button leaveButton = new Button();
  TextField messageField = new TextField(80);
  Button sendButton = new Button();
  Button emptyButton = new Button();

  public UDPChat() {
    try  {
      jbInit();
      leaveButton.setEnabled(false);
      sendButton.setEnabled(false);
	  textArea.setEditable(false);
      pack();
      show();
    }
    catch(Exception e) {
      e.printStackTrace();
    }
  }

  public static void main(String[] args) {
    UDPChat uDPChat = new UDPChat();
  }

  private void jbInit() throws Exception {
    this.setTitle("多点传送数据报聊天程序 - IP地址范围: 224.0.0.1 ~ 239.255.255.255");
    this.addWindowListener(new java.awt.event.WindowAdapter() {

      public void windowClosing(WindowEvent e) {
        this_windowClosing(e);
      }
    });
    ipLabel.setText("IP:");
    ipField.setText("225.0.0.1");
    portLabel.setText("端口:");
    portField.setText("4000");
    nameLabel.setText("用户名:");
    nameField.setText("匿名");
    joinButton.setForeground(Color.blue);
    joinButton.setLabel("进入");
    joinButton.addActionListener(new java.awt.event.ActionListener() {
      public void actionPerformed(ActionEvent e) {
        join();
      }
    });
    leaveButton.setForeground(Color.red);
    leaveButton.setLabel("离开");
    leaveButton.addActionListener(new java.awt.event.ActionListener() {
      public void actionPerformed(ActionEvent e) {
        leave();
      }
    });
    messageField.setText("这里输入要发送的文字");
    messageField.addActionListener(new java.awt.event.ActionListener() {
       public void actionPerformed(ActionEvent e) {
        send();
      }
    });
    sendButton.setLabel("    发送    ");
    sendButton.addActionListener(new java.awt.event.ActionListener() {
      public void actionPerformed(ActionEvent e) {
        send();
      }
    });
    emptyButton.setLabel("清空记录");
    emptyButton.addActionListener(new java.awt.event.ActionListener() {

      public void actionPerformed(ActionEvent e) {
        emptyButton_actionPerformed(e);
      }
    });
    this.add(configPanel, BorderLayout.NORTH);
    configPanel.add(ipLabel);
    configPanel.add(ipField);
    configPanel.add(portLabel);
    configPanel.add(portField);
    configPanel.add(nameLabel);
    configPanel.add(nameField);
    this.add(messagePanel, BorderLayout.SOUTH);
    messagePanel.add(messageField);
    messagePanel.add(sendButton);

    this.add(textArea, BorderLayout.CENTER);
	Panel p = new Panel();
	p.setLayout(new GridBagLayout());
	GridBagConstraints c = new GridBagConstraints();
	c.weightx = c.weighty = 1;c.fill = GridBagConstraints.HORIZONTAL;
	c.gridx = 0; c.gridy = 0;
	p.add(joinButton, c);
	c.gridy ++;
	p.add(leaveButton, c);
	c.gridy ++;
	p.add(emptyButton, c);
    this.add(p, BorderLayout.WEST);
  }

  void join() {
    username = nameField.getText();
    if(username.equals("")) {
      textArea.append("请你务必首先输入一个名字.\n");
      return;
    }
    try {
      textArea.append("尝试进入聊天室...\n");
      group = InetAddress.getByName(ipField.getText());
	  port = Integer.parseInt(portField.getText());
      socket = new MulticastSocket(port);
      socket.joinGroup(group);
      String message = username +  "[" + InetAddress.getLocalHost() + "] 进入聊天室 " + group + "! 端口号"
        + portField.getText() + ".\n";
      DatagramPacket hi = new DatagramPacket(message.getBytes(),
        message.getBytes().length, group, port);
      socket.send(hi);
      nameField.setEditable(false);
      joinButton.setEnabled(false);
      leaveButton.setEnabled(true);
      sendButton.setEnabled(true);
      new ReaderThread().start();
    }catch(Exception ex) {
      textArea.append("无法进入聊天室:" + ex + "\n");
	  ex.printStackTrace();
    }
  }

  void send() {
    if(socket == null) return;
    try {
      String message = username + "[" + InetAddress.getLocalHost() + "] : " + messageField.getText() + "\n";
      DatagramPacket hi = new DatagramPacket(message.getBytes(),
        message.getBytes().length, group, port);
      socket.send(hi);
	  messageField.requestFocus();
	  messageField.selectAll();
    }catch(Exception ex) {
      textArea.append("无法发送消息:" + ex + "\n");
    }
  }

  void leave() {
    if(socket == null) return;
    try {
      textArea.append("尝试离开聊天室...");
      String message = username + " 已经离开了聊天室 " + group  + "!\n";
      DatagramPacket hi = new DatagramPacket(message.getBytes(),
        message.getBytes().length, group, port);
      socket.send(hi);
      socket.leaveGroup(group);
      socket.close();
      socket = null;
      nameField.setEditable(true);
      joinButton.setEnabled(true);
      leaveButton.setEnabled(false);
      sendButton.setEnabled(false);
	  textArea.append("你已经离开了聊天室!\n");
    }catch(Exception ex) {
      textArea.append("无法离开聊天室:" + ex + "\n");
	  ex.printStackTrace();
    }
  }

  void this_windowClosing(WindowEvent e) {
    leave();
    System.exit(0);
  }
  
  class ReaderThread extends Thread {

    public void run() {
      while(socket != null) {
        try {
          byte[] buf = new byte[1024];
          DatagramPacket recv = new DatagramPacket(buf, buf.length);
          socket.receive(recv);
          textArea.append(new String(recv.getData()));
        }catch(Exception ex) {
        }
      }
    }

  }

  void emptyButton_actionPerformed(ActionEvent e) {
    textArea.setText("");
  }

}