Abusing C# language, checking various language specific behaviors.
There are two sets of projects (client + server) that you can play with. They all live in this same solution file. You can run a pair at this same time by specifying Solution -> Properties -> Startup Project -> Multiple Startup Project. And choose client/server pair or more then that.
The websocket sharp pair is using websocket sharp library to be more precise it is using it's .net core clone - because the original library only works on .NET Framework.