Adding an audio only flow to the signaling server

The WebSocket-based signaling server we developed in node.js was designed in an abstract way, so that it only used call_token to route signals from one user to another. Other than that, it doesn't have any specific dependencies upon the contents or type of signaling messages at all. This means that no updates to the signaling server are required to adapt it to support audio only calls.

The only change required is to update the name of the source HTML file it reads in using the fs package. Just change this to basic_audio_call.html to match our new HTML user interface:

fs.readFile("basic_audio_call.html", function(error, data) {

Once you have made this simple change, just restart the signaling server; for example, by typing node webrtc_signal_server.js on the command line, and then you are ready to start making your audio only call.