The FHIRcast Hub project is an implementation of a FHIRcast Hub with some additional APIs to make it easy to inspect and test with.
Assuming your current directory is the same as this file, you can run the Hub using:
$ dotnet run
which will launch the Hub on http://localhost:5000 by default.
There are some APIs outside of FHIRcast that can be used towards the hub to inspect its current state:
Get the current subscriptions of the hub.