How to return a message when calling by a TCP connection?

Question

I am working on a communication between Android and Arduino board.

The Android makes a TCP connection with the board and successfully sends some strings to the board.

The problem is, there is an int in my Arduino code (e.g. int distance) and I would like to pass that back to my Android device.

I have handled the Android side already, but I do not know how to return a message from Arduino.

in = new BufferedReader(new InputStreamReader(socket.getInputStream()));

                //in this while the client listens for the messages sent by the server
                while (mRun) {
                    serverMessage = in.readLine();

                    if (serverMessage != null && mMessageListener != null) {
                        //call the method messageReceived from MyActivity class
                        mMessageListener.messageReceived(serverMessage);
                    }
                    serverMessage = null;

                }

This is the Android side code but I think that it is not a specific Android problem, there should be some way for Arduino to make a response of an integer variable (without concern what is the source device)?

What I should do in Arduino for making that response?

Answer 1

I'm assuming that you are using an Ethernet shield, as nothing about this is stated. But solution is really similar between many network solution.

Once a TCP connection has been established, it can be used like you would use the Serial;

you'll probably end up having something similar to:

EthernetClient client = server.available(); //accept a new connection
if (client) { //if valid connection
  client.print(distanceValue);
  client.close(); //close connection
}

look at the official API reference for a more detailed list of available command.