It seems nothing groundbreaking. A router, some middleware and websockets.
Also, nim is a mess. Very poorly designed language. I tried it a couple of years ago and was repelled by its syntax and attempts to solve every single problem for you.
Nim is just right down ugly and borrowed the worst from Pascal and Python. The multi-paradigm concept is a mess. Tried it a couple of years ago and moved on to better, more simple tools.