WebRTC simple datachannel example?

I am very interested by the webrtc technology. I found some great example for video sharing like this one, made very simple and easy to understand.

However, it seems quite impossible to find a very simple, light, easy to understand example of how to make it work for data channels.

I checked this one, tried to change it with my "custom signaling server" (or whatever is the name) created from this example, but I am not able to use data channels.

My question is: Is there, somewhere, a very simple example about data channels, not in the same browser? If not, can someone provide some code?

Thanks (and happy christmas!)