How to organize the transfer of an audio stream from a phone to a tablet?

Question

Android

Hello!
I am writing an application for myself, I use the tablet as CarPC and I would like to make it possible to connect via bluetooth from a phone (any OS) to an Android 6.0 tablet using the A2DP profile in order to play music through my application installed there. Pairing with devices works and the profile is programmatically enabled (according to the log), but I can't catch the audio stream. In general, here are the questions:
1. How can I understand what I am transferring from one device to another audio stream?
2. How to catch and decode an audio stream?
3. Do I need to somehow force the tablet to use the A2DP profile? (the phone does not display this profile, although another device - a wireless speaker - displays this profile)