Java 组播

MulticastSocketServer.java

 package cn.edu.buaa.multicast;

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

 /**
  * One thing that we need to take into consideration here, is that there are
  * specific addresses that allow us to use a MulticastSocket are limited,
  * specifically in the range of 224.0.0.0 to 239.255.255.255. Some of them are
  * reserved, like 224.0.0.0. The address that we are using, 224.0.0.3, can be
  * used safely.
  */
 public class MulticastSocketServer {

     final static String INET_ADDR = "224.0.0.3";
     final static int PORT = 8888;

     public static void main(String[] args) throws UnknownHostException, InterruptedException {
         // Get the address that we are going to connect to.
         InetAddress addr = InetAddress.getByName(INET_ADDR);

         // Open a new DatagramSocket, which will be used to send the data.
         try (DatagramSocket serverSocket = new DatagramSocket()) {
             for (int i = 0; i < 5; i++) {
                 String msg = "Sent message no " + i;

                 // Create a packet that will contain the data
                 // (in the form of bytes) and send it.
                 DatagramPacket msgPacket = new DatagramPacket(msg.getBytes(), msg.getBytes().length, addr, PORT);
                 serverSocket.send(msgPacket);

                 System.out.println("Server sent packet with msg: " + msg);
                 Thread.sleep(500);
             }
         } catch (IOException ex) {
             ex.printStackTrace();
         }
     }
 }

MulticastSocketClient.java

 package cn.edu.buaa.multicast;

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

 public class MulticastSocketClient {
     final static String INET_ADDR = "224.0.0.3";
     final static int PORT = 8888;

     public static void main(String[] args) throws UnknownHostException {
         // Get the address that we are going to connect to.
         InetAddress address = InetAddress.getByName(INET_ADDR);

         // Create a buffer of bytes, which will be used to store
         // the incoming bytes containing the information from the server.
         // Since the message is small here, 256 bytes should be enough.
         byte[] buf = new byte[256];

         // Create a new Multicast socket (that will allow other sockets/programs
         // to join it as well.
         try (MulticastSocket clientSocket = new MulticastSocket(PORT)) {
             // Joint the Multicast group.
             clientSocket.joinGroup(address);

             while (true) {
                 // Receive the information and print it.
                 DatagramPacket msgPacket = new DatagramPacket(buf, buf.length);
                 clientSocket.receive(msgPacket);

                 String msg = new String(buf, 0, buf.length);
                 System.out.println("Socket 1 received msg: " + msg);
             }
         } catch (IOException ex) {
             ex.printStackTrace();
         }
     }
 }