Check that TURN / STUN works

We need to configure a network with a strict firewall to test from:

BigBlueButton normally requires a wide range of UDP ports to be available for WebRTC communication. In some network restricted sites or development environments, such as those behind NAT or a firewall that restricts outgoing UDP connections, users may be unable to make outgoing UDP connections to your BigBlueButton server.

Going forward, when users connect behind a restrictive firewall that prevents outgoing UDP connections, the TURN server will enable BigBlueButton to connect to FreeSWITCH and Kurento via the TURN server through port 443 on their firewall.

https://docs.bigbluebutton.org/2.2/setup-turn-server.html