CreateServerSocket.java

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class CreateServerSocket implements Runnable {

    private int port;
    private boolean running;
    private ServerSocket ss = null;
    private Map<Integer, List<Socket>> clientMap = new HashMap<>();

    public CreateServerSocket(int port) {
        this.port = port;
    }

    public void start() {
        try {
            ss = new ServerSocket(port);
        } catch (IOException e) {

        }
        running = true;
        new Thread(this).start();
    }

    @Override
    public void run() {
            try {
                while (true) {
                    Socket socket = ss.accept();
                    if (clientMap.get(port) != null) {
                        List<Socket> list = clientMap.get(port);
                        list.add(socket);
                        clientMap.put(port, list);
                    } else {
                        List<Socket> list = new ArrayList<>();
                        list.add(socket);
                        clientMap.put(port, list);
                    }
                    System.out.println("accepted at port " + port + socket);

                    //start another client thread for each server 
                    (new ServerClientThread(socket, clientMap.get(port))).start();

                }
            } catch(IOException e){

            }
    }
}