App to connect to java socket on laptop

EyeSight

Hi I am starting off making apps, and as a test i'm sending a string from my android to a java socket server running on my laptop. both are connected to the same wifi but i will want it to work on 3g and other wifis also

here is my java code:

//makes a socket listening on port 4242
            ServerSocket serverSocket = new ServerSocket(4242);
            System.out.println("RUNNING");
            String output;

            while(true){
                Socket socket = serverSocket.accept();
                
                InputStreamReader streamReader = new InputStreamReader(socket.getInputStream());
                BufferedReader reader = new BufferedReader(streamReader);
                
                output = reader.readLine();
                System.out.println(output);                
            }    

snippet of code not executing in android app:

  public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.final_year_project);                
        try{
            //connect to socket(server)   
            Socket socket = new Socket("<my_ipaddress>", 4242);
            //Socket socket = new Socket("10.0.2.2", 4242);
            
            //for writing to server
            DataOutputStream outToServer = new                  DataOutputStream(socket.getOutputStream());
           
            outToServer.writeBytes(output + '\n');

            socket.close();
        }
        catch(Exception ex){
            ex.printStackTrace();
        }
    }

android permissions:

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

This works on the emulator if i use the 10.0.2.2 address, nothing works on the phone. i assume i have to do some port forwarding? can somebody please talk me through it please?