Make AudioDecoder Listener static interface.
Add ability to listen to ACK frames.
Implement stop and wait. Still need to send ACKs.
Send ACKs on receipt of frames. Implement stopping wait.

Still need to check whether data is on the line before sending and implement exponential backoff.
Create exponential backoff logic in sending class.

* Still need to implement logic in AudioDecoder.
Implement isLineFree method.