组播技术 和 JGroups

IP数据包传输类型
    IPv4定义了3种IP数据包的传输：
    单播（unicast）
    广播（broadcast）
    组播（multicast）.

    比较一下unicast和multicast两种数据的传输方式可以发现，
    当一台主机向多个用户发送信息时，单播对于每一个用户都
    要发送一份数据的拷贝，而组播总共只需发送一份数据的拷贝。
    这样，组播的使用就大大的节省了带宽，减轻了网络的负载，
    从而更加有效的利用了网络的带宽资源.

    IP组播和单播的目的地址不同，IP组播的目的地址是组地址.
    是从224.0.0.0到239.255.255.255之间的D类IP地址，其中
    224.0.0.0到224.0.0.255是被保留的地址,224.0.0.1表示子
    网中所有的组播组, 224.0.0.2表示子网中的所有路由器，
    224.0.0.5表示OSPF（Open Shortest Path First）路由器,
    224.0.0.6表示OSPF指定路由器，224.0.0.12表示DHCP服务器.

    在D类地址的分配中，IETF建议遵循以下的原则：
        全球范围：224.0.1.0～238.255.255.255；
        有限范围：239.0.0.0～239.255.255.255；
        本地站点范围：239.253.0.0～239.253.0.16
        本地机构范围：239.192.0.0～239.192.0.14.

 

 

Java 组播程序的例子

import java.io.IOException;import java.net.DatagramPacket;import java.net.InetAddress;import java.net.MulticastSocket;import java.net.NetworkInterface;public class Learn2 {public static void main(String[] args) throws IOException {    new MulticastServer().start();    new MulticastClient().start();  }}class MulticastServer extends Thread{public void run(){    try{   MulticastSocket mcastSocket = new MulticastSocket(7777);   InetAddress inetAddress = InetAddress.getByName("230.0.0.1");   mcastSocket.setNetworkInterface(NetworkInterface.getByInetAddress(InetAddress.getLocalHost()));   mcastSocket.joinGroup(inetAddress);         while (true) {    byte [] arb = new byte [100];    DatagramPacket datagramPacket = new DatagramPacket(arb, arb.length);    mcastSocket.receive(datagramPacket);    System.out.println("Server:"+new String(arb,0,datagramPacket.getLength()));        }  }catch(Exception dx){   dx.printStackTrace();  }}}class MulticastClient extends Thread{public void run(){    try{   while(true){    byte [] arb = new byte []{'h', 'e', 'l', 'l', 'o'};    InetAddress inetAddress = InetAddress.getByName("230.0.0.1");    DatagramPacket datagramPacket = new DatagramPacket(arb, arb.length, inetAddress, 7777);    MulticastSocket multicastSocket = new MulticastSocket();    multicastSocket.send(datagramPacket);        Thread.sleep(1000);   }  }catch(Exception dx){   dx.printStackTrace();  }}}

 

基于JGROUPS 的例子：

import java.io.BufferedReader;import java.io.InputStreamReader;import org.jgroups.Address;import org.jgroups.ChannelException;import org.jgroups.JChannel;import org.jgroups.Message;import org.jgroups.ReceiverAdapter;import org.jgroups.View;public class Learn1 {  private JChannel channel = null;  public Learn1() throws ChannelException{  channel = new JChannel("c:/udp.xml"); }  public static void main(String[] args) throws ChannelException {  Learn1 learn = new Learn1();    learn.startup();    new SendMessage(learn.channel).start(); }   private void startup() throws ChannelException{  channel.setReceiver(new ReceiverMessage());  //channel.setOpt(option, value);  channel.connect("FL"); }}class ReceiverMessage extends ReceiverAdapter{ public void receive(Message msg) {  System.out.println(msg.getSrc() + ": " + msg.getObject()+" at "+System.currentTimeMillis()); }   public void viewAccepted(View new_view) {  System.out.println("viewAccepted: " + new_view);   }   public void suspect(Address suspected_mbr) {  System.out.println("suspect: " + suspected_mbr);    } }class SendMessage extends Thread{   private JChannel channel;  public SendMessage(JChannel channel){  this.channel = channel; }   public void run(){   BufferedReader in=new BufferedReader(new InputStreamReader(System.in));  while(true) {   try{    System.out.print("> "); System.out.flush();    String line=in.readLine().toLowerCase();    if(line.startsWith("quit") || line.startsWith("exit")) {     System.exit(0);    }    Message msg=new Message(null, null, line);    channel.send(msg);   }catch(Exception dx){    dx.printStackTrace();   }  } }}

 

 

使用的 udp.xml 及相关 参数说明