Transfering files via an RTCDataChannel connection

The model here is the same as interacting with signaling_server, except in this case the data is flowing directly to the other peer instead via the WebSocket server.

To send some data you simply call the data_channel.send() function just as you call the signaling_server.send() function.

And to handle receiving the data you set up a data_channel.onmessage handler, just like you set up the signaling_server.onmessage handler.

In this way, the core usage of the two API's is almost identical. It is only the underlying network implementation that really differs.