简单易懂的组播（课本）

1，不断重复广播一则新闻。

packageMulSocket.fromBook;

importjava.net.*;

publicclassBroadCastextendsThread{
Strings="今天天气好晴朗，处处好风光！";
intport=5858;//组播的端口
InetAddressgroup=null;//组播组
MulticastSocketsocket=null;//多点广播套接字

BroadCast(){
try{
group=InetAddress.getByName("239.255.8.0");//设置组播组为239.255.8.0
socket=newMulticastSocket(port);//多点广播套接字将在port端口广播
socket.setTimeToLive(0);//多点广播套接字发送数据报范围为本地网络
socket.joinGroup(group);
//加入组播组,加入group后，socket发送的数据报可以被加入到group中的成员接收到
}catch(Exceptione){
}
}

publicvoidrun(){
while(true){
try{
DatagramPacketpacket=null;//待广播的数据报
bytedata[]=s.getBytes();
packet=newDatagramPacket(data,data.length,group,port);
System.out.println(newString(data));
socket.send(packet);//广播数据报
sleep(2000);
}catch(Exceptione){
System.out.println(e.toString());
break;
}
}
}

publicstaticvoidmain(Stringargs[]){
newBroadCast().start();
}
}

2加入组播组，接收广播数据

packageMulSocket.fromBook;

importjava.net.*;
importjava.awt.*;
importjava.awt.event.*;
importjavax.swing.*;

publicclassReceiveextendsJFrameimplementsRunnable,ActionListener{
privatestaticfinallongserialVersionUID=1L;
intport;//组播的端口
InetAddressgroup=null;//组播组的地址
MulticastSocketsocket=null;//多点广播套接字

JButtonstartReceive,stopReceive;
JTextAreashowArea;
Threadthread;//负责接收信息的线程
booleanstop=false;

publicReceive(){
super("定时接收信息");
thread=newThread(this);
startReceive=newJButton("开始接收");
stopReceive=newJButton("停止接收");
startReceive.addActionListener(this);
stopReceive.addActionListener(this);
showArea=newJTextArea(10,10);
JPanelnorth=newJPanel();
north.add(startReceive);
north.add(stopReceive);
Containercon=getContentPane();
con.add(north,BorderLayout.NORTH);
con.add(newJScrollPane(showArea),BorderLayout.CENTER);
port=5858;
try{
//初始化一气呵成
group=InetAddress.getByName("239.255.8.0");
socket=newMulticastSocket(port);
socket.joinGroup(group);
}catch(Exceptione){
}
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setSize(320,300);
validate();
setVisible(true);
}

publicvoidactionPerformed(ActionEvente){
if(e.getSource()==startReceive){
if(!(thread.isAlive())){
thread=newThread(this);
stop=false;
}
try{
thread.start();
}catch(Exceptionee){
}
}
if(e.getSource()==stopReceive){
stop=true;
}
}

publicvoidrun(){
while(true){
bytedata[]=newbyte[8192];
DatagramPacketpacket=null;
packet=newDatagramPacket(data,data.length,group,port);
try{
socket.receive(packet);
Stringmessage=newString(packet.getData(),0,packet
.getLength());
showArea.append("/n"+message);
showArea.setCaretPosition(showArea.getText().length());
}catch(Exceptione){
}
if(stop==true)
break;
}
}

publicstaticvoidmain(Stringargs[]){
newReceive();
}
}

思路明确简单易懂。