Good morning!
Ready to work on your project. I have a big experience in developing of servers and clients RTC (real-time communications). Implemented streaming server for broadcasting television and client to server.
I propose to implement WebRTC-server. Clients will be Web-application and native GUI (QT, it will give cross-platform Windows, Linux, Mac OS X).
WebRTC-server can be implemented in one of two options:
Java - for a small number of clients (up to 50) is completely working solution, but if you get more clients you'll need to buy expensive server. Easy maintenance code (ready to develop it hereinafter).
++ async - high-performance server, doesn’t have limits in implementation of additional functional, there is no need to buy expensive servers. For code maintenance you need to have C ++ professional (ready to develop it hereinafter).