Bluetooth reference or tutorial for Codey Rocky



I want to write an Android application which can send Bluetooth messages to Codey Rocky.
So far I’ve not found any help.
This is only I’ve got, but it’s five years old code and it has nothing useful for Codey:

I know there is official Android app, my son loves it. But I’d like to know and use all off possibilities with Bluetooth.
Just like as wifi/IR with python.

Currently I’m working on an application based on ASP.Net web API which provides commands for Codey by wifi connection.
I want something similar with Android+bluetooth.

Best regards