How to check if WebRTC uses a relay server?
webrtc
Solution
When you establishing WebRTC connection, you set STUN and/or TURN for a web browser to use. If you informed a web browser with the both options, web browser will start trying to use STUN first. Then, in case of unsuccess it will try to use TURN.
The 'relay server' is a TURN-server.
As I know, there is no standard way to know out which option a web browser decided to use: STUN or TURN.
In other hand, if you're the owner of TURN server, you can see whether web client does use it or not, and then send this information to the client.
UPDATED
This is my code: https://github.com/fycth/webrtcexample/blob/master/www/js/rtc_lib.js
You can see there I use just STUN server, so it is p2p or nothing, and no relay.
Problem
I read that WebRTC uses relay servers, if the direct peer connection doesn't work because of firewalls. Is there a way to check, if this is the case?