There are many complicated issues involved with the correct working of WebRTC across domains, NATS, geographies, and so on. It is important for now that the firewall of a system, or any kind of port-blocking policy, should be turned off to be able to make a successful audio-video WebRTC call across any two parties that are not on the same Local Area Network (LAN).

For the user to not have to switch the firewall off, we need to configure the Simple Traversal of UDP through NAT (STUN) server or modify the Interactive Connectivity Establishment (ICE) parameter in the SDP exchanged. STUN helps in packet routing of devices behind a NAT firewall. STUN only helps in device discoverability by assigning publicly accessible addresses to devices within a private local network.

Traversal Using Relay NAT (TURN) servers also serve to accomplish the task of interconnecting the endpoints behind NAT. As the name suggests, TURN forces media to be proxied through the server...