I have a Server Application running on a Raspberry Pi. That piece of code basically listens on a TCP socket for a client (Android Java App) to connect to it. Once the client is connected it shares data with the client (state of valves, parameters, etc.). The client on the other hand is able to send commands and parameters to the Server which then performs certain actions (controling actuators).
There can be more than one client but no more than e.g. 10.
Now I had that setup running for quite a time but was never sure if I have choosen the right architectural approach regarding the client’s software architecture and the way the communication between server and client is built.
My questions:

1. Is a TCP connection the proper approach for that briefly described usecase?
2. What should the Android App’s software architecture roughly look like?

Any hints?