Java 组播

MulticastSocketServer.java

 1 package cn.edu.buaa.multicast;
 2 
 3 import java.io.IOException;
 4 import java.net.DatagramPacket;
 5 import java.net.DatagramSocket;
 6 import java.net.InetAddress;
 7 import java.net.UnknownHostException;
 8 
 9 /**
10  * One thing that we need to take into consideration here, is that there are
11  * specific addresses that allow us to use a MulticastSocket are limited,
12  * specifically in the range of 224.0.0.0 to 239.255.255.255. Some of them are
13  * reserved, like 224.0.0.0. The address that we are using, 224.0.0.3, can be
14  * used safely.
15  */
16 public class MulticastSocketServer {
17 
18     final static String INET_ADDR = "224.0.0.3";
19     final static int PORT = 8888;
20 
21     public static void main(String[] args) throws UnknownHostException, InterruptedException {
22         // Get the address that we are going to connect to.
23         InetAddress addr = InetAddress.getByName(INET_ADDR);
24 
25         // Open a new DatagramSocket, which will be used to send the data.
26         try (DatagramSocket serverSocket = new DatagramSocket()) {
27             for (int i = 0; i < 5; i++) {
28                 String msg = "Sent message no " + i;
29 
30                 // Create a packet that will contain the data
31                 // (in the form of bytes) and send it.
32                 DatagramPacket msgPacket = new DatagramPacket(msg.getBytes(), msg.getBytes().length, addr, PORT);
33                 serverSocket.send(msgPacket);
34 
35                 System.out.println("Server sent packet with msg: " + msg);
36                 Thread.sleep(500);
37             }
38         } catch (IOException ex) {
39             ex.printStackTrace();
40         }
41     }
42 }

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MulticastSocketClient.java

 1 package cn.edu.buaa.multicast;
 2 
 3 import java.io.IOException;
 4 import java.net.DatagramPacket;
 5 import java.net.InetAddress;
 6 import java.net.MulticastSocket;
 7 import java.net.UnknownHostException;
 8 
 9 public class MulticastSocketClient {
10     final static String INET_ADDR = "224.0.0.3";
11     final static int PORT = 8888;
12 
13     public static void main(String[] args) throws UnknownHostException {
14         // Get the address that we are going to connect to.
15         InetAddress address = InetAddress.getByName(INET_ADDR);
16 
17         // Create a buffer of bytes, which will be used to store
18         // the incoming bytes containing the information from the server.
19         // Since the message is small here, 256 bytes should be enough.
20         byte[] buf = new byte[256];
21 
22         // Create a new Multicast socket (that will allow other sockets/programs
23         // to join it as well.
24         try (MulticastSocket clientSocket = new MulticastSocket(PORT)) {
25             // Joint the Multicast group.
26             clientSocket.joinGroup(address);
27 
28             while (true) {
29                 // Receive the information and print it.
30                 DatagramPacket msgPacket = new DatagramPacket(buf, buf.length);
31                 clientSocket.receive(msgPacket);
32 
33                 String msg = new String(buf, 0, buf.length);
34                 System.out.println("Socket 1 received msg: " + msg);
35             }
36         } catch (IOException ex) {
37             ex.printStackTrace();
38         }
39     }
40 }

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