Android client not connecting to server KryoNet

I am trying to connect from an Android client (from my phone) to a server (my PC). Both the server and the client are using KryoNet. The connection is succesful when I try to connect from a client which is on the same PC as the server. The connection is also succesful when i try to connect from my Android phone connected to wireless (to the same router as the PC which runs the server). The connection fails when i try to connect from the phone while using mobile data (it gives a timeout error). I did port forwarding and opened the port from Windows firewall setting. Any idea what's wrong?

Client code:

final Client client = new Client();     
        client.getKryo().register(StringRequest.class);
        final StringRequest request = new StringRequest();
        new Thread(client).start();

        System.out.println("Client started.");

        try {
            client.connect(5000, ipAddress, 54555);
            client.addListener(new Listener() {
                public void received(Connection connection, Object object) {
                    if (object instanceof StringRequest) {
                        StringRequest response = (StringRequest) object;
                        Gdx.app.log("Client",response.data);
                    }
                }
            });
        } catch (IOException e) {
            Gdx.app.log("Exception", e.getMessage());
            e.printStackTrace();
        }
        request.data = "Hello";
        client.sendTCP(request);

Server code:

Server server = new Server();
    Kryo kryo = server.getKryo();
    kryo.register(StringRequest.class);
    server.start();
    try {
        server.bind(54555);
    } catch (IOException e) {
        e.printStackTrace();
    }
    server.addListener(new Listener() {
        public void received (Connection connection, Object object) {
           if (object instanceof StringRequest) {
              StringRequest request = (StringRequest)object;
              System.out.println("Server"+request.data);
              StringRequest response = new StringRequest();
              response.data = "response";
              connection.sendTCP(response);
           }
        }
     });

Does your Android application have the Internet permission?

<uses-permission android:name="android.permission.INTERNET" /> 

It is needed to communicate over the network. Also, make sure you are trying to connect with your PC's external IP, not local IP (192.168.x.xxx). You can get your external IP here.