https://appr.tc is down. How to set up own signaling server/ room server URL?
The source code of apprtc remains available on github: https://github.com/webrtc/apprtc
You might want to read this blog post about whether to use it though: https://bloggeek.me/webrtc-signaling-server-not-use-apprtc/ The project has been effectively abandoned for years and you will have a hard time finding support.