The service uses Nancy(http://nancyfx.org) for the web layer, and NModbus4 (https://github.com/NModbus4/NModbus4) for the Modbus layer. The service makes use of Nancy's self hosting capabilities so the API is self hosted. The code in theory should support Holding registers, Input registers, Coils, and Inputs. It should also support Modbus TCP, Serial RTU and serial ASCII. However, I don't have enough devices to test all these modes.