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();
        }
    }
}