communicationclient.java

利用UDP实现网络聊天室

package communicationclient;

import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import javax.swing.*;
import java.net.*;
import java.io.*;

/**
 * Title:        客户端UDP通讯Applet程序
 * Description:  用于客户端，实现与服务器端UDP通讯
 * Copyright:    Copyright (c) 2002
 * Company:      北京师范大学计算机系
 * @author 孙一林
 * @version 1.0
 */

public class CommunicationClient extends Applet {
  boolean isStandalone = false;
  JLabel jLabel1 = new JLabel();
  JTextArea jTextArea1 = new JTextArea();
  JLabel jLabel2 = new JLabel();
  JTextField jTextField1 = new JTextField();
  private DatagramSocket sendSocket,receiveSocket;//声明发送数据报Socket和接收数据报Socket
  private DatagramPacket sendPacket,receivePacket;//声明发送数据报文包和接收数据报文包

  /**Get a parameter value*/
  public String getParameter(String key, String def) {
    return isStandalone ? System.getProperty(key, def) :
      (getParameter(key) != null ? getParameter(key) : def);
  }

  /**Construct the applet*/
  public CommunicationClient() {
  }
  /**Initialize the applet*/
  public void init() {
    try {
      jbInit();
    }
    catch(Exception e) {
      e.printStackTrace();
    }
  }
  /**Component initialization*/
  private void jbInit() throws Exception {
    jLabel1.setText("通讯记录：");
    jLabel1.setBounds(new Rectangle(16, 9, 68, 27));
    this.setLayout(null);
    jTextArea1.setText("你好！");
    jTextArea1.setBounds(new Rectangle(15, 48, 349, 59));
    jLabel2.setText("输入通讯内容：");
    jLabel2.setBounds(new Rectangle(17, 125, 92, 37));
    jTextField1.setText("通讯内容");
    jTextField1.setBounds(new Rectangle(127, 129, 244, 31));
    jTextField1.addActionListener(new java.awt.event.ActionListener() {
      public void actionPerformed(ActionEvent e) {
        jTextField1_actionPerformed(e);
      }
    });
    this.add(jLabel1, null);
    this.add(jTextArea1, null);
    this.add(jLabel2, null);
    this.add(jTextField1, null);
  }
  /**Start the applet*/
  public void start() {
    waitForPackets();
  }
  /**Stop the applet*/
  public void stop() {
  }
  /**Destroy the applet*/
  public void destroy() {
  }
  /**Get Applet information*/
  public String getAppletInfo() {
    return "Applet Information";
  }
  /**Get parameter info*/
  public String[][] getParameterInfo() {
    return null;
  }

  /**方法waitForPacket用来监听来自于服务器的数据报，当获得数据报后，在文本显示区域显示出来*/
  public void waitForPackets(){
    try{
      sendSocket=new DatagramSocket();//实例化一个发送数据报Socket对象
      receiveSocket= new DatagramSocket(8001);//实例化一个接收数据报Socket对象，以8001为端口
    }
    catch (SocketException e){//捕获异常
      jTextArea1.append("不能打开数据报Socket，或数据报Socket无法与指定端口连接!");
    }
    while (true){
      try{
        byte buf[]=new byte[100];
        receivePacket=new DatagramPacket(buf,buf.length);//实例化一个接收数据报文包对象
        receiveSocket.receive(receivePacket);//以receivePacket为参数，接收数据包
        jTextArea1.append("\n服务器：\t");
        byte[] data=receivePacket.getData();
        String receivedString=new String(data);
        jTextArea1.append(receivedString);//将接收到的数据包中的数据显示出来
      }
      catch(IOException e){
        jTextArea1.append("网络通讯出现错误，问题在"+e.toString());
      }
    }
  }

  /**Main method*/
  public static void main(String[] args) {
    CommunicationClient applet = new CommunicationClient();
    applet.isStandalone = true;
    Frame frame;
    frame = new Frame() {
      protected void processWindowEvent(WindowEvent e) {
        super.processWindowEvent(e);
        if (e.getID() == WindowEvent.WINDOW_CLOSING) {
          System.exit(0);
        }
      }
      public synchronized void setTitle(String title) {
        super.setTitle(title);
        enableEvents(AWTEvent.WINDOW_EVENT_MASK);
      }
    };
    frame.setTitle("Applet Frame");
    frame.add(applet, BorderLayout.CENTER);
    applet.init();
    applet.start();
    frame.setSize(400,320);
    Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
    frame.setLocation((d.width - frame.getSize().width) / 2, (d.height - frame.getSize().height) / 2);
    frame.setVisible(true);
  }

  void jTextField1_actionPerformed(ActionEvent e) {
    try{
      jTextArea1.append("\n客户端：");
      String string=jTextField1.getText();
      jTextArea1.append(string);
      byte[] databyte=new byte[100];
      string.getBytes(0,string.length(),databyte,0);
      sendPacket=new DatagramPacket(databyte,string.length(),InetAddress.getByName("202.112.88.31"),8000);//发送数据报，其中IP为主机服务器IP地址
      sendSocket.send(sendPacket);
    }
    catch(IOException ioe){
      jTextArea1.append("网络通讯出现错误，问题在"+ioe.toString());
    }
  }
}