I've created a new, way better networking solution, RiptideNetworking, along with improved tutorials on how to use it.
This is the source code for my C# networking tutorial series on YouTube.
Each branch contains the code corresponding to what you should have at the end of each video in the series.
Note: using the console app server in the GameServer project (from any branch) with the GameClient project from branch 6 and up will produce errors. This is because after part 5 of the series, we moved the server code into Unity and stopped updating the console server.
Unity Version: 2018.3.7