Java-UDP程序编写（实现组播）

1.播报广播端

package test;

import java.net.DatagramPacket;
import java.net.InetAddress;
import java.net.MulticastSocket;

public class Weather extends Thread{
	String weather = "今晚团建";
	int port = 9898;
	InetAddress ipAddress = null;
	MulticastSocket socket = null;
	/**
	 * 创建广播数据的主机，广播的主机和接收广播的主机必须加入到同一组，
	 * 地址范围是224.0.0.0~224.255.255.255
	 */
	
	
	Weather(){					//构造方法
		try {
			ipAddress = InetAddress.getByName("224.255.10.0");
			socket = new MulticastSocket(port);			//实例化多点广播套接字
			socket.setTimeToLive(1);				//指定发送范围是本地网络
			socket.joinGroup(ipAddress);   			//加入广播组
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	
	public void run() {
		while (true) {
			DatagramPacket packet = null;			//声明datagrampacket对象
			byte data[] = weather.getBytes();     //将字符串转化为字节数组
			packet = new DatagramPacket(data, data.length,ipAddress,port);			//将字节数组封装进数据包里
			System.out.println(new String(data));    //将字节数组转化为字符串打印在控制台
			try {
				socket.send(packet);			//发送数据包
				sleep(3000);
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
	}
	
	public static void main (String[] args) {
		Weather w = new Weather();		//创建本类对象
		w.start();						//启动线程
	}
}

2.接收广播端

package test;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.net.DatagramPacket;
import java.net.InetAddress;
import java.net.MulticastSocket;

import javax.swing.Action;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.WindowConstants;

public class Receive extends JFrame implements Runnable,ActionListener{  		//实现runable,actionlistener接口
	int port;
	InetAddress groupAddress = null;
	MulticastSocket multicastSocket = null;
	JButton startButton = new JButton("开始接收");
	JButton stopButton = new JButton("结束接收");
	JTextArea inceAr = new JTextArea(5,10);
	JTextArea inced = new JTextArea(5,10);
	Thread thread;
	boolean b = false;
	/**
	 * 接收广播端
	 */
	
	public Receive () {
		super("客户端接收");   						//继承,设置窗口标题为客户端接收
		setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
		thread = new Thread(this);
		startButton.addActionListener(this);
		stopButton.addActionListener(this);
		inceAr.setForeground(Color.blue);
		inced.setForeground(Color.red);					//设置文字的颜色
		JPanel jPanel = new JPanel();
		JPanel jPanel2 = new JPanel();
		JScrollPane jScrollPane = new JScrollPane(inced);   //将文字域添加进滚动面板
		jPanel.add(startButton);
		jPanel.add(stopButton);
		jPanel2.add(jScrollPane,BorderLayout.WEST);
		jPanel2.add(inceAr,BorderLayout.EAST);
		add(jPanel,BorderLayout.SOUTH);
		add(jPanel2,BorderLayout.CENTER);
		validate();								//刷新，如果之前设置了大小，会刷新成为设置的大小
		port = 9898;
		try {
			groupAddress = InetAddress.getByName("224.255.10.0");
			multicastSocket = new MulticastSocket(port);		//绑定多点广播套接字
			multicastSocket.joinGroup(groupAddress);
		} catch (Exception e) {
			e.printStackTrace();
		}
		setBounds(0,0,400,200);			//设置布局
		setVisible(true);				//将布局设置为显示状态
	}
	
	public void run() {
		while (true) {
			byte[] data = new byte[1024];
			DatagramPacket packet = null;
			packet = new DatagramPacket(data, data.length,groupAddress,port);					//将字节数组封装进数据包
			try {
				multicastSocket.receive(packet);
				String messageString = new String(packet.getData(),0,packet.getLength());  		//将数据包里的数据转化为字符串
				inceAr.setText("正在接收的内容是：\n"+messageString);			//设置正在接收文字内容域
				inced.append(messageString + "\n");				//设置为每条信息为一行
//				validate();
				System.out.println("asasas");
			} catch (Exception e) {
				e.printStackTrace();
			}
			
			if (b == true) {
				break;						//当变量为true时退出循环
			}   
			
		}
	}
	public void actionPerformed(ActionEvent e) {
		if (e.getSource() == startButton) {
			startButton.setBackground(Color.red);
			stopButton.setBackground(Color.yellow);
			if (! (thread.isAlive())) {
				thread = new Thread(this);
			}
			thread.start();					//启动线程
		}
		if (e.getSource() == stopButton) {
			startButton.setBackground(Color.yellow);
			stopButton.setBackground(Color.red);
			b = true;
		}
	}
	
	public static void  main(String[] args) {
		Receive receive = new Receive();
//		receive.setSize(400,200);
	}
}

3.接收端接收广播数据
<1>广播端开启
<2>接收端开启