一、MulticastSocket类
多播也称为组播，就是给一组特定的主机(多播组)发送数据。多播通过多播数据报套接MulticastSocket类来实现
重要的构造方法：
MulticastSocket() 创建多播套接字
MulticastSocket(int port) 创建多播套接字并将其绑定到特定端口
MulticastSocket(SocketAddress bindaddr) 创建绑定到指定套接字地址的MulticastSocket
常用的方法：
void joinGroup(InetAddress meastaddr) 加入多播组
void leaveGroup(InetAddress meastaddr) 离开多播组
void send(DatagramPacket p) 从此套接字发送数据包
public void receive(DatagramPacket p) 从此套接字接收数据包
二、代码实现
发送端程序设计：发送端将在广播地址为“230.198.112.0”，9876号端口处发送广播信息
package org.multicastsocket;
import java.net.InetAddress;
import java.net.DatagramPacket;
import java.net.MulticastSocket;
public class multicastDemo01 extends Thread
{
String message[] = {"失物招领：有谁在操场丢失钥匙一串，请到学校广播站认领。","大风蓝色预警：预计今天下午有北风6级，请有关单位和人员做好防范准备。"};
int port = 9876;//组播的端口
InetAddress group = null;//组播的组地址
MulticastSocket mutiSocket = null;//组播套接字
public multicastDemo01()
{
try
{
group = InetAddress.getByName("230.198.112.0");//设置广播组地址
mutiSocket = new MulticastSocket(port);//多点广播套接字将在port端口广播
mutiSocket.setTimeToLive(1);
mutiSocket.joinGroup(group);
}
catch (Exception e)
{
System.out.println("Error:"+e);
}
}
public void run()
{
while(true)
{
try
{
DatagramPacket packet = null;
for(String msg : message)//循环发送每条广播信息
{
byte buff[] = msg.getBytes();
packet = new DatagramPacket(buff, buff.length,group,port);
System.out.println(new String(buff));
mutiSocket.send(packet);
sleep(2000);
}
}
catch (Exception e)
{
System.out.println("Error:"+e);
}
}
}
public static void main(String[] args)
{
new multicastDemo01().start();
}
}
接收端程序设计：接收端主机将加入广播地址为“230.198.112.0”，并在9876号端口处接收广播信息
package org.multicastsocket;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.net.InetAddress;
import java.net.DatagramPacket;
import java.net.MulticastSocket;
public class multicastDemo02 extends JFrame implements Runnable,ActionListener
{
private static final long serialVersionUID = -5923790809266120014L;
int port;
InetAddress group = null;
MulticastSocket socket = null;
JButton startButton;
JButton stopButton;
JButton cleanButton;
JTextArea currentMsg;
JTextArea receiveMsg;
Thread thread;
boolean isStop = false;//停止接收广播信息的标志
public multicastDemo02()
{
setTitle("接收广播信息");
Container container = this.getContentPane();
startButton = new JButton("开始接收");
stopButton = new JButton("停止接收");
cleanButton = new JButton("清空信息");
startButton.addActionListener(this);
stopButton.addActionListener(this);
cleanButton.addActionListener(this);
currentMsg = new JTextArea(3,20);//创建3行20列的多行文本框
currentMsg.setForeground(Color.red);//设置字体颜色为红色
receiveMsg = new JTextArea(8,20);//默认字体颜色为黑色
container.setLayout(new BorderLayout());
JSplitPane sp = new JSplitPane(JSplitPane.VERTICAL_SPLIT);//创建一带水平分隔条的面板
JScrollPane currScrollPane = new JScrollPane();
currScrollPane.setViewportView(currentMsg);
JScrollPane recvScrollPane = new JScrollPane();
recvScrollPane.setViewportView(receiveMsg);
currentMsg.setEditable(false);
receiveMsg.setEditable(false);
sp.add(currScrollPane);
sp.add(recvScrollPane);
container.add(sp,BorderLayout.CENTER);
JPanel bottomJPanel = new JPanel();
bottomJPanel.add(startButton);
bottomJPanel.add(stopButton);
bottomJPanel.add(cleanButton);
container.add(bottomJPanel,BorderLayout.SOUTH);
setSize(500,400);
setVisible(true);
thread = new Thread(this);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
port = 9876;
try
{
group = InetAddress.getByName("230.198.112.0");
socket = new MulticastSocket(port);
socket.joinGroup(group);
}
catch (Exception e)
{
}
}
public void actionPerformed(ActionEvent e1)
{
if(e1.getSource() == startButton)
{
startButton.setEnabled(false);
stopButton.setEnabled(true);
if(!(thread.isAlive()))
{
thread = new Thread(this);
}
try
{
thread.start();
isStop = false;
}
catch (Exception ee)
{
}
}
if(e1.getSource() == stopButton)
{
startButton.setEnabled(true);
stopButton.setEnabled(false);
isStop = true;
}
if(e1.getSource() == cleanButton)
{
receiveMsg.setText("");
}
}
public void run()
{
while(true)
{
byte buff[] = new byte[8192];
DatagramPacket packet = null;
packet = new DatagramPacket(buff, buff.length,group,port);
try
{
socket.receive(packet);
String message = new String(packet.getData(),0,packet.getLength());
currentMsg.setText("正在接收的内容：\n"+message);
receiveMsg.append(message+"\n");
}
catch (Exception e)
{
}
if(isStop == true)
{
break;
}
}
}
public static void main(String[] args)
{
new multicastDemo02();
}
}
三、 效果展示
