This is a slightly less basic TCP server that hands off each connection to a runner. This project exists as an example for ElixirSips Episode 205 - The Opposite of Mocks.
You should be able to clone this app and run it with:
iex -S mix
At that point, the app is running on port 8112 (or whatever is setup in the config/config.exs file). You can open a TCP connection to it, and it will be a basic upcasing echo TCP server.