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?

• Chris Stratton: The binary representation of integers varies between Arduino (16 bit) and Android (32) bit, and while both an Arduino and most native-level Android implementations are little-endian, Android java code is big-endian. So transferring your values in a string format may ease compatibility, as well as making it easy to debug the system by substituting a terminal emulator.

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.