built in Server Side Web Service

Question

I would like to create a C# application that listens to a Local port/socket, filters a client submitted URL string, respond, as well as run some server side code, using something very similar to this API...  http://www.vmix.com.au/help12/index.htm?DeveloperAPI.html

http://127.0.0.1:8088/api/?Function=Fade&Duration=1000

Could someone please point me in the proper direction to start learning this process?

I don't expect it to be easy, but searching for this information isn't either, as I'm not sure I'm searching the correct keywords.

Although this is a C# website, C++ would also be acceptable.

Thanks for your assistance.