package meeting;import java.awt.*;import java.awt.event.*;import javax.swing.*;import java.net.*;class Listener extends Thread{//用來監(jiān)聽端口消息的線程		DatagramPacket packet;	MulticastSocket socket;	TextArea textArea;	    Listener(MulticastSocket socket1,TextArea textArea1){		byte[] data = new byte[512];		packet = new DatagramPacket(data,data.length);			socket = socket1;		textArea = textArea1;		}		public void run(){	  String message;	  	      while(true){//不斷的監(jiān)測端口是否有新的消息       	try    	{      		packet.setData(new byte[512]);                      //設(shè)定接收數(shù)據(jù)的DatagramPacket實(shí)例的數(shù)組大小      		packet.setLength(512);                               //設(shè)定接收數(shù)據(jù)的DatagramPacket實(shí)例的長度      		socket.receive(packet);                              //通過MulticastSocket實(shí)例端口從組播組接收數(shù)據(jù)      		message = new String(packet.getData(), 0, packet.getLength());  //將接受的數(shù)據(jù)轉(zhuǎn)換成字符串形式      		textArea.append("\n" + message);    	}    	catch(Exception e1)    	{      		System.out.println("no new message,please wait" );                   //捕捉異常情況    	}      }  	}}public class MeetingMGFrame extends JFrame{  private JPanel contentPane;  private TextField textField1 = new TextField();//輸入要發(fā)送的消息  private TextField textField2 = new TextField();//輸入組播組地址  private TextField textField3 = new TextField();//輸入用戶名  private Button button1 = new Button();//發(fā)送消息按鈕  private Button button2 = new Button();//進(jìn)入組播組按鈕  private Label label1 = new Label();//提示輸入消息  private Label label2 = new Label();//顯示組播組信息  private Label label3 = new Label();//提示輸入用戶名  private TextArea textArea1 = new TextArea();//顯示組播組傳來的消息  int port;                                       //聲明組播使用的端口  MulticastSocket socket;                          //聲明建立組播組使用的MulticastSocket類  InetAddress group;                               //聲明建立組播組使用的組播組地址  DatagramPacket packet;                           //聲明發(fā)送和接收數(shù)據(jù)所使用的DatagramPacket類  String user = new String();						//聲明用戶名  boolean connected = false;						//是否連接的標(biāo)志符  public MeetingMGFrame() {    enableEvents(AWTEvent.WINDOW_EVENT_MASK);    try {      toInit();    }    catch(Exception e) {      e.printStackTrace();    }  }    private void toInit() throws Exception  {//初始化窗體    contentPane = (JPanel) this.getContentPane();            //設(shè)計(jì)窗體布局    contentPane.setLayout(null);    this.setSize(new Dimension(400, 400));    this.setTitle("組播實(shí)現(xiàn)網(wǎng)絡(luò)會議");    textField1.setBounds(new Rectangle(90,260,200,20));    textField2.setBounds(new Rectangle(90,20,65,20));    textField3.setBounds(new Rectangle(210,20,80,20));    textField2.setText("224.0.0.1");    label1.setBounds(new Rectangle(20, 260, 60, 20));    label2.setBounds(new Rectangle(10, 20, 60, 20));    label3.setBounds(new Rectangle(160,20,40,20));    label1.setText("輸入消息：");    label2.setText("輸入組播組ip:");    label3.setText("用戶名");    textArea1.setBounds(new Rectangle(20,60,320,180));    textArea1.setEditable(false);    button1.setLabel("發(fā)送消息");    button1.setBounds(new Rectangle(300, 260, 60, 20));    button1.addActionListener(new java.awt.event.ActionListener() {      public void actionPerformed(ActionEvent e) {        button1_actionPerformed(e);      }    });    button2.setLabel("進(jìn)入會議");    button2.setBounds(new Rectangle(300, 20, 60, 20));    button2.addActionListener(new java.awt.event.ActionListener() {      public void actionPerformed(ActionEvent e) {        button2_actionPerformed(e);      }    });    contentPane.add(textField1, null);    contentPane.add(textField2,null);    contentPane.add(textField3,null);    contentPane.add(button1, null);    contentPane.add(button2,null);    contentPane.add(label1, null);    contentPane.add(label2,null);    contentPane.add(label3,null);    contentPane.add(textArea1,null);  }    protected void processWindowEvent(WindowEvent e) {    super.processWindowEvent(e);    if (e.getID() == WindowEvent.WINDOW_CLOSING) {      System.exit(0);    }  }    public void createMulticastGroupAndJoin()           //創(chuàng)建一個(gè)組播組并加入該組  {  	String str1 = new String();  	String str2 = new String();  	str1 = textField2.getText();  	str2 = textField3.getText();  	  	if(str1.compareTo("") != 0 && str2.compareTo("") != 0 ){    	try    	{    		user = str2;									   //獲取用戶名      		port = 1234;                                      //設(shè)置組播組的監(jiān)聽端口      		group = InetAddress.getByName(textField2.getText());       //設(shè)置組播組的地址為224.0.0.1      		socket = new MulticastSocket(port);               //初始化MulticastSocket類并將端口號與之關(guān)聯(lián)      		socket.joinGroup(group);                           //加入此組播組      		label2.setText("進(jìn)入組播組：");						//提示已經(jīng)進(jìn)入組播組      		connected = true;      		    	}    	catch(Exception e1)    	{      		System.out.println("Error1: " + e1);               //捕捉異常情況	   	}		byte[] data = new byte[512];		packet = new DatagramPacket(data, data.length, group, port);    //初始化DatagramPacket的實(shí)例    		try  		{				String str = new String();    		str = user +"進(jìn)入組播組：" + textField2.getText();		//字符串形式的用戶進(jìn)入組的消息    		data = str.getBytes();       						//將所要發(fā)送的數(shù)據(jù)轉(zhuǎn)換為字節(jié)形式并存儲在數(shù)組中    		packet.setData(data);				  				//將字節(jié)形式的消息放入packet    		socket.send(packet);                                       //通過MulticastSocket實(shí)例端口向組播組發(fā)送數(shù)據(jù)  		}   	 	catch(Exception e)  		{  			System.out.println("Error2:" + e);  		}			Listener listener = new Listener(socket,textArea1);  	//初始化偵聽端口用的線程		listener.start();									    //激活線程	  }//end of if   	 else{		  textArea1.setText("請確認(rèn)輸入組播組的ip地址和您的用戶名"); 	  }	  }  public void sendData()                                //向組播組發(fā)送數(shù)據(jù)的函數(shù)  {    try    {      String str = new String();      str = user +":" + textField1.getText();      byte[] data = str.getBytes();       				//將用戶所要發(fā)送的數(shù)據(jù)轉(zhuǎn)換為字節(jié)形式并存儲在數(shù)組中      packet.setData(data);				  				//將字節(jié)形式的消息放入packet      socket.send(packet);                                   //通過MulticastSocket實(shí)例端口向組播組發(fā)送數(shù)據(jù)    }    catch(Exception e1)    {      System.out.println("Error3: " + e1);                   //捕捉異常情況    }  }  void button1_actionPerformed(ActionEvent e) {  	sendData();                                             //向組播組發(fā)送數(shù)據(jù)  }    void button2_actionPerformed(ActionEvent e){  	if(!connected){  		createMulticastGroupAndJoin();  	}  	else{  		textArea1.append("\n已經(jīng)建立連接，請發(fā)送消息");	  	}  }}