Help with socket error 'connection refused: connect'

I'm trying to make a client-server application, this is the client code:

try {
            Socket socket = new Socket("192.168.1.66", 9999);
            PrintWriter salida = new PrintWriter(new OutputStreamWriter(socket.getOutputStream()), true);
            salida.println("Up");
            salida.close();
        } catch (UnknownHostException e) {
            JOptionPane.showMessageDialog(null, e.getMessage());
        } catch (IOException e1) {
            JOptionPane.showMessageDialog(null, e1.getMessage());
        }

And this one on the server:

public void run() {
        try {
            ServerSocket servidor = new ServerSocket(9999);
            while (true) {
                Socket socket = servidor.accept();
                BufferedReader entrada = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                String order = entrada.readLine();
                System.out.println(order);
                if (order.equals("Up")) {
                    upScore();
                    socket.close();
                } else if (order.equals("Down")) {
                    downScore();
                    socket.close();
                }
            }
        } catch (IOException e) {
            System.out.println(e.getMessage());
        }
    }

I already made sure that port '9999' is open on my modem.