Presentity (.NET SDK)

A Presence and Signaling SDK for .NET. It allows to connect multiple computers in a single conference over the Internet. Of course, a user can be part of multiple conferences at the same time.

Here is a demo (VB.NET)

Presentity Demo (for server API v2)
Presentity Demo (for server API v1)

Options:

Free (for ever): Public servers, no SSL (unlimited users, unlimited conferences, unlimited messages, shared bandwidth).
SSL ($800 one time): SSL on public servers.
Isolated Instance ($2400 one time): Dedicated bandwidth, ability to mix SSL and non-SSL users in a single conference.

Contact me by email handcode@outlook.com or here https://www.upwork.com/freelancers/~015a6b6dbddab22502 if you are interested.