java - 在 JAVA 中将 UDP 服务器连接到客户端

Question

我有一个服务器和一个客户端(比如 client1)，它们都在一个文件上，工作得很好。我遇到这样的情况:我有另一个客户端(比如 client2)向服务器发送信息。该服务器必须将从 client2 获取的信息发送到 client1。但是当我在服务器和客户端1上使用相同的端口号和相同的IP地址时，当我尝试从客户端2发送信息时，客户端1也同时接受。

如何从 client2 发送信息，以便第一个服务器首先接受它，然后将该信息发送到 client1？

客户端2代码:

import java.io.*;
import java.net.*;

class Client1
{

    public static void main(String[] args)throws Exception {

        try {
                InetAddress ip=InetAddress.getByName("228.5.6.7");
            int port=4270;

            MulticastSocket sock=new MulticastSocket();
            String msg="Hello All";

            DatagramPacket packet;
           while(true)
          {
            packet =new DatagramPacket(msg.getBytes(),msg.length(),ip,port);
            sock.send(packet);
           }

      } 
     catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } 

    }

}

我的服务器和客户端代码:

class Server implements Runnable
{

    public void run()
    {
        try
        {       
            //get the multicast ip
            InetAddress ip = InetAddress.getByName("228.5.6.7");

            int port=4270;
             byte[] buffer=new byte[100];
             byte[] data = null; 

            MulticastSocket sock=new MulticastSocket(port);

            //join the multicast group
            sock.joinGroup(ip);
            while(true)
            {
                //create a datagram packet in which u will receive the msg  

                Thread.sleep(2000);  
                DatagramPacket pack=new DatagramPacket(buffer,buffer.length);
                sock.receive(pack);
                String msg = new String(buffer);              
                System.out.println("Sever Has Received :" +msg);

               //SENDING THE MESSAGE TO CLIENT
               System.out.println("Sending the Message!!!");


               data = msg.getBytes(); 
               DatagramPacket pack1 = new DatagramPacket(data,msg.length(),ip,port);
               Thread.sleep(2000); 
               sock.send(pack1);
            }

        }
         catch (Exception ex) {
         Thread t = Thread.currentThread();
         t.getUncaughtExceptionHandler().uncaughtException(t, ex);
         }

    }
  }

客户端1代码:

class Client implements Runnable
{

    public void run()
    {

       try {
       InetAddress address1 = InetAddress.getByName("228.5.6.7");
       int port=4271;
       MulticastSocket socket1 = new MulticastSocket(port);
      //join a Multicast group and send the group salutations
       socket1.joinGroup(address1);
       byte[] data1 = new byte[256];
       DatagramPacket packet1 = new DatagramPacket(data1,data1.length);
       while(true)
      {                                
       // receive the packets 
       socket1.receive(packet1); 
       String str = new String(packet1.getData(),0,packet1.getLength());
       Thread.sleep(2000);
       System.out.println("Client Received : "+str);
      }  
    }
      catch (Exception ex) {
      Thread t = Thread.currentThread();
      t.getUncaughtExceptionHandler().uncaughtException(t, ex);
     }
   }    
 }  

主程序

class ClientAndServer
{

   public static void main(String[] args)
   {

      Server s = new Server();

     //First start Server and then Start client
     Thread t1 = new Thread(s);
      t1.start();
      Client c = new Client();
     Thread t2 = new Thread(c);

        t2.start();
     }
}  

Answer 1

由于您使用 MulticastSocket 链接 Client1 <-> Server <-> Client2。如果服务器发送一条消息，每个客户端都会收到它，这是来自 MulticastSocket doc

When one sends a message to a multicast group, all subscribing recipients to that host and port receive the message

如果您不希望这样，您可能需要使用两个不同的套接字，使用两个端口

• 端口1:客户端1 <-> 服务器
• 端口2:客户端2 <-> 服务器

然后您可以将消息仅重定向到一个或另一个端口，但将有两个不同的消息 channel