多播聊天程序不会接收消息

Question

我目前正在尝试创建一个使用Proxy和Subject Observer模式的多播聊天程序，但我无法让它工作。我目前的问题是代理主题和具体主题没有沟通。我知道，代码有点粗糙，但在这里。

代理主题

package client;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.MulticastSocket;
import java.net.UnknownHostException;
import java.util.Vector;

import sitted.Message;
import sitted.Observer;
import sitted.Server;
import sitted.Subject;

public class ChatSubjectProxy implements Subject{
    MulticastSocket sock;
    DatagramSocket sendSock;
    Vector<Observer> observers = new Vector<Observer>();
    InetAddress ADDRESS;
    int sendPort, recvPort;
    public ChatSubjectProxy(InetAddress address, int recvPort, int sendPort){
        this.sendPort = sendPort;
        this.recvPort = recvPort;
        try {
            sendSock = new DatagramSocket();
            ADDRESS = address;
            sock = new MulticastSocket(recvPort);
            sock.joinGroup(ADDRESS);

            Thread t = new Thread(){
                public void run(){
                    String msg = "";
                    while(true){
                        try {
                            byte[] buffer = new byte[1024];
                            DatagramPacket packet = new DatagramPacket(buffer,buffer.length);
                            sock.receive(packet);
                            msg= new String(packet.getData());
                            if(msg!=null){
                                notifyObservers(recieve(msg));
                            }
                        } catch (IOException e) {
                            notifyObservers(new Message("SERVER","IO EXCEPTION: LOCAL PROXY"));
                            e.printStackTrace();
                        }                   
                    }
                }
            };
            t.start();



        } catch (UnknownHostException e) {      
            notifyObservers(new Message("SERVER","UNKNOWN HOST EXCEPTION: LOCAL PROXY"));
            e.printStackTrace();
        } catch (IOException e) {
            notifyObservers(new Message("SERVER","IO EXCEPTION: LOCAL PROXY"));
            e.printStackTrace();
        }
    }
    @Override
    public void remove(Observer obs) {
        observers.remove(obs);      
    }

    @Override
    public void add(Observer obs) {
        observers.add(obs);     
    }

    @Override
    public void notifyObservers(Message msg) {
        for(Observer obs: observers){
            obs.update(msg);
        }       
    }
    @Override
    public void send(Message msg) {
        String s = msg.getUser()+","+msg.getMessage();
        byte[] buffer = s.getBytes();
        System.out.println(s);
        try {
            DatagramPacket packet = new DatagramPacket(buffer,buffer.length,ADDRESS,sendPort);
            sendSock.send(packet);
        } catch (IOException e) {
            notifyObservers(new Message("SERVER","IO EXCEPTION: LOCAL PROXY"));
            e.printStackTrace();
        }

    }
    public Message recieve(String s){
        String token[] = s.split(",",2);
        return(new Message(token[0],token[1]));     
    }
}


package server;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.Socket;
import java.util.Vector;

import sitted.Message;

具体主题

public class ChatSubject{
    Vector<Message> log = new Vector<Message>();
    Vector<Socket> sockets = new Vector<Socket>();
    Vector<BufferedReader> readers = new Vector<BufferedReader>();
    Vector<PrintWriter> writers = new Vector<PrintWriter>();
    String name;
    PrintWriter writer;
    DatagramSocket socket;
    InetAddress address;
    InetAddress returnAddr;
    int port;
    int sendPort;

    public ChatSubject(String name, InetAddress address){
        this.name = name;
        this.address = address;
        try {
            socket = new DatagramSocket(0);     

            port = socket.getLocalPort();   
            System.out.println("SUBJECT PORT: "+port);
            DatagramSocket temp = new DatagramSocket(0);
            sendPort = temp.getLocalPort();
            temp.setReuseAddress(true);
            temp.close();

            Thread t = new Thread(){
                public void run(){
                    while(true){
                        try {
                            byte[] buffer = new byte[1024];
                            DatagramPacket packet = new DatagramPacket(buffer,buffer.length);
                            socket.receive(packet);
                            returnAddr = packet.getAddress();
                            receiveMessage(new String(packet.getData()));                           
                        }catch (IOException e) {
                            e.printStackTrace();
                            sendMessage("SERVER: IO EXCEPTION");
                        }
                    }   

                }
            };
            t.start();
        } catch (IOException e) {
            sendMessage("SERVER: IO EXCEPTION");
            e.printStackTrace();
        }
    }
    public void receiveMessage(String s) throws IOException{
        String token[] = s.split(",",2);
        log.add(new Message(token[0],token[1]));
        System.out.println(new Message(token[0],token[1]));
        sendMessage(s);
    }
    public void sendMessage(String s){

        try {
            byte[] buffer = s.getBytes();
            DatagramPacket packet = new DatagramPacket(buffer,buffer.length,returnAddr,sendPort);
            socket.send(packet);    
        } catch (IOException e) {
            e.printStackTrace();
            sendMessage("SERVER: IO EXCEPTION");
        }


    }
    public String getName(){
        return name;
    }
    public InetAddress getAddress(){
        return address;
    }
    public int getSendPort(){
        return sendPort;
    }
    public int getRecvPort(){
        return port;
    }


}