Question

我在同一主机上同时运行服务器和客户端的Messenger程序（Mac Pro PC）。服务器和客户端之间的单播连接在同一主机上按预期工作。客户端通过单播连接向服务器发送消息。服务器将消息发送到多播地址。客户端侦听多播地址，并假设从服务器接收消息。

多播连接无法正常工作。服务器无例外地发送消息，但客户端没有通过多播接收消息。这是发送方和接收方的代码段。

public interface SocketMessengerConstants 
{   
// address for multicast datagrams
public static final String MULTICAST_ADDRESS = "239.0.0.1";

// port for listening for multicast datagrams
public static final int MULTICAST_LISTENING_PORT = 5555;

// port for sending multicast datagrams
public static final int MULTICAST_SENDING_PORT = 5554; 
......   

public class MulticastSender implements Runnable
{   
  private byte[] messageBytes; // message data

  public MulticastSender( byte[] bytes ) 
  {  
   messageBytes = bytes; // create the message
  } // end MulticastSender constructor

   // deliver message to MULTICAST_ADDRESS over DatagramSocket
  public void run() 
  {  
   try // deliver message
   {         
     // create DatagramSocket for sending message
     DatagramSocket socket = 
        new DatagramSocket( MULTICAST_SENDING_PORT );

     // use InetAddress reserved for multicast group
     InetAddress group = InetAddress.getByName( MULTICAST_ADDRESS );

     // create DatagramPacket containing message
     System.out.println(messageBytes.length);
     DatagramPacket packet = new DatagramPacket( messageBytes, 
        messageBytes.length, group, MULTICAST_LISTENING_PORT );

     socket.send( packet ); // send packet to multicast group
     socket.close(); // close socket
    } // end try
    catch ( IOException ioException ) 
    { 
     ioException.printStackTrace();
    } // end catch
  } // end method run
} // end class MulticastSender


public class PacketReceiver implements Runnable 
{
 private MessageListener messageListener; // receives messages
 private MulticastSocket multicastSocket; // receive broadcast messages
 private InetAddress multicastGroup; // InetAddress of multicast group
 private boolean keepListening = true; // terminates PacketReceiver

 public PacketReceiver( MessageListener listener ) 
 {
  messageListener = listener; // set MessageListener

  try // connect MulticastSocket to multicast address and port 
  {
     // create new MulticastSocket
     multicastSocket = new MulticastSocket(
        MULTICAST_LISTENING_PORT );

     // use InetAddress to get multicast group
     multicastGroup = InetAddress.getByName( MULTICAST_ADDRESS );

     // join multicast group to receive messages
     multicastSocket.joinGroup( multicastGroup ); 

     // set 5 second timeout when waiting for new packets
     multicastSocket.setSoTimeout( 5000 );
   } // end try
   catch ( IOException ioException ) 
   {
     ioException.printStackTrace();
   } // end catch
  } // end PacketReceiver constructor

 // listen for messages from multicast group 
 public void run() 
 {          
  // listen for messages until stopped
  while ( keepListening ) 
  {
     // create buffer for incoming message
     byte[] buffer = new byte[ MESSAGE_SIZE ];

     // create DatagramPacket for incoming message
     DatagramPacket packet = new DatagramPacket( buffer, 
        MESSAGE_SIZE );

     try // receive new DatagramPacket (blocking call)
     {            
        multicastSocket.receive( packet ); 
     } // end try
     catch ( SocketTimeoutException socketTimeoutException ) 
     {
        continue; // continue to next iteration to keep listening
     } // end catch
     catch ( IOException ioException ) 
     {
        ioException.printStackTrace();
        break;
     } // end catch

     // put message data in a String
     String message = new String( packet.getData() );

     message = message.trim(); // trim whitespace from message
     System.out.println(message);

     // tokenize message to retrieve user name and message body
     StringTokenizer tokenizer = new StringTokenizer( 
        message, MESSAGE_SEPARATOR );

     // ignore messages that do not contain a user 
     // name and message body
     if ( tokenizer.countTokens() == 2 ) 
     {
        // send message to MessageListener
        messageListener.messageReceived( 
           tokenizer.nextToken(), // user name
           tokenizer.nextToken() ); // message body
     } // end if
   } // end while

   try 
   {
     multicastSocket.leaveGroup( multicastGroup ); // leave group
     multicastSocket.close(); // close MulticastSocket
   } // end try
   catch ( IOException ioException )
   { 
     ioException.printStackTrace();
   } // end catch
} // end method run

......
} // end class PacketReceiver

路由器上的多播功能已禁用。我从路由器的网关中取消选中“禁用IGMP代理”。但是仍然没有收到多播数据报包。

更新：程序位于防火墙后面。防火墙允许传入连接后，一切都会按预期进行。

组播数据报报文未删除

0 个答案: