Java Client - Server - Client with synchronised thread

Well, since i posted it i guess i can aswer it too.

So, it's not a perfect solution (in my opinion) and i'm not totally done with it, but it seems to work so far.

For the first problem (how to retrieve another client Socket), i'm creating a static hashtable on server side, with the client name as key and the socket as value. Whenever a client connect, he's added to this table; and when he disconnects he's deleted (i didn't try the disconnect part)

private static Hashtable<String,Socket> connectedClients= new Hashtable<String, Socket>();
public static void setConnectedClient(String username, Socket clientSocket) {
    connectedClients.put(username, clientSocket);
}

public static void disconnectClient(String user) {
    connectedClients.remove(user);
}

So wherever i am in the program on server side, i can retrieve a client socket (knowing his username).

For the second problem (how to avoid mixup witht he other client work with the server) i'm creating a second socket. Which mean, on client side there's two socket: one for communication with server, and one for communication with clients (coming from the server) on another port. Which mean i also have another server socket on server side for this other port. So, when a client connect to the server, this second socket is created on client & server side.

        Socket TCHATSocket = Server.getServerSocket().accept(); //create a new socket specifically for TCHAT
        Server.setConnectedClient(user, TCHATSocket); //register the client ID & TchatSocket in the list of connected clients.

Now, on client side i must keep listening for any input from this socket (in case another client want to communicate with me through the server) but not when i'm doing stuff with the server.

To do that, i create another thread on client side. When the client connect, it launch the thread which create the second socket and wait for an input from the server. But, when the client launch any function which involve communication with server, this thread is paused, and then unpaused at the end of the function. Here is the thread class:

package client;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;

public class TCHAT extends Thread{
    private InputStream in;
    private OutputStream out;
    private Socket pakeSocket;
    private String message;
    private volatile boolean pause = false;

    public void pause() {
        pause = true;
    }

    public void unPause() {
        pause = false;
        synchronized(this) {
            notify();
        }

    }

    public TCHAT() {
        try {
            tchatSocket = new Socket(InetAddress.getLocalHost(),2004);
            in = tchatSocket.getInputStream();
            out = tchatSocket.getOutputStream();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    public void run(){
        while(!tchatSocket.isClosed()) {

            if(pause) {
                System.out.println("TCHAT paused");
                synchronized (this) {
                    try {
                        wait();// wait until someone calls notify() (by calling the method unPause)
                    }catch (InterruptedException e) {           
                        e.printStackTrace();            
                    }
                }
            }

            else {
                System.out.println("Waiting for TCHAT demand");
                try {
                    BufferedReader br = new BufferedReader(new InputStreamReader(in));
                    message = br.readLine();
                    System.out.println(message);
                    //Find a way to blok the while after receiving the message:
                    tchatSocket.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }


        }
    }

}

As you can see, it's not really terminated: for now i just get a message from server and then close the socket; but i guess you can do whatever you want before closing it. Plus, for some reason, i never get the "TCHAT paused" message when i call pause(), and i don't get another "Waiting for TCHAT demand" when i unpause, but it seems to work (since without the pause the others clients functions won't work, and here they work well, and the client correctly receive the message from server even after uploading or whatever.)

basically, when i want to use a client function, i just do:

TCHAT.pause();
upload(file); //or any function involving client/server communication
TCHAT.unpause();

Hope it'll help someone, but still happy to make it work :)