Use peer-to-peer protocol to broadcast your video over 20+ users.
This module simply initializes socket.io and configures it in a way that single audio/video/screen stream can be shared/relayed over unlimited users without any bandwidth/CPU usage issues. Everything happens peer-to-peer!
Check this thread or this github repository.
You can write iOS or Android apps for this demo as well.
Install following Android app and join broadcasts from this demo: https://play.google.com/store/apps/details?id=com.webrtc.scalablebroadcast