java实现UDP广播数据报

要求:

主机不断地重复播出节目预报，可以保证加入到同一组的主机随时可以接收到广播信息。

Server代码:

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.InetAddress;
import java.net.MulticastSocket;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextArea;

public class ServerDemo2 extends JFrame implements Runnable,ActionListener{

//UDP实现广播数据报
//加入同一个组中的主机随时都可以接收到信息
private static int port;
private static InetAddress group = null;
private JButton button_begin;
private JButton button_stop;
private JTextArea textArea_1;
private JTextArea textArea_2;
private Thread thread;
private MulticastSocket socket = null;
private boolean flag = false;
public ServerDemo2(){
setTitle("UDP实现广播数据报");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100,50,360,380);
JPanel panel = new JPanel(new FlowLayout());
button_begin = new JButton("开始接收");
panel.add(button_begin);
button_begin.addActionListener(this);
button_stop = new JButton("停止接收");
panel.add(button_stop);
button_stop.addActionListener(this);

getContentPane().add(panel,BorderLayout.NORTH);

JPanel panel_1 = new JPanel(new GridLayout(1, 2));
textArea_1 = new JTextArea();
textArea_1.setLineWrap(true);
panel_1.add(textArea_1);
textArea_2 = new JTextArea();
textArea_2.setLineWrap(true);
panel_1.add(textArea_2);

getContentPane().add(panel_1,BorderLayout.CENTER);
thread = new Thread(this);
validate();//刷新
port = 9898;
try {
group = InetAddress.getByName("224.255.10.0");
socket = new MulticastSocket(port);
socket.joinGroup(group);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public static void main(String[] args) {
ServerDemo2 server = new ServerDemo2();
server.setVisible(true);
}
@Override
public void actionPerformed(ActionEvent e) {
if(e.getSource() == button_begin){
if(!thread.isAlive()){
thread = new Thread(this);
}
thread.start();
flag = false;
}
if(e.getSource() == button_stop){
flag = true;
}
}
@Override
public void run() {
while(true){
byte[] buff = new byte[1024];
DatagramPacket packet = null;
packet = new DatagramPacket(buff, 0, buff.length);
try {
socket.receive(packet);
String message = new String(packet.getData(),0,packet.getLength());
textArea_1.setText("正在接收的内容:\n"+message);
textArea_2.append(message+"\n");
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if(flag){
break;
}
}
}
}

Client客户端代码:

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.InetAddress;
import java.net.MulticastSocket;
import java.net.UnknownHostException;

public class ClientDemo2 extends Thread{

private String weather = "节目预告:八点钟有大型晚会，请收听.";
private int port = 9898;
InetAddress address = null;
MulticastSocket socket = null;
public ClientDemo2(){
try {
address = 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(address);//加入广播组
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void run(){
while(true){
DatagramPacket packet = null;
byte[] buff = weather.getBytes();
packet = new DatagramPacket(buff, buff.length,address,port);
System.out.println(new String(buff));
try {
socket.send(packet);
sleep(3000);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
public static void main(String[] args) {
ClientDemo2 client = new ClientDemo2();
client.start();
}
}

说明:要广播或接受广播的主机必须加入到一个组内，地址在224.0.0.0-224.255.255.255之间。这类地址并不代表某个特定主机的位置。加入到同一个组的主机可以在某个端口上广播信息， 也可以在某个端口接受信息。