To call a function from a client with a netconnection, you have to use a Flash application. There is a great working reference for this in the Wowza install-dir example folder: ServerSideModules. This includes a Flash application and server-side module and shows just about every way to communicate and pass data between Flash and Wowza.
To interface with Wowza from an application server like .net using a server page like aspx, you need a HTTProvider. This is a good starting place for that:
http://community.wowza.com/t/-/245
There are other HTTProviders that might be useful reference in the same forum section:
http://community.wowza.com/c/-/10
Richard