Here ya go,
I really have no idea. I think you can do both peer to peer or everyone talks to a server. Ajax, and Sockets are where you need to look. You can also pass things to the commandline with node-webkit so you can probably issue SSH and FTP commands too, if the firewall lets you through.
Compliments of Goolge, and using the search term Scirra rather than Construct 2.
Looking forward to the day we can start using the built in forum search again.
If you think finding multiplayer info is hard, try finding a regex tutorial with google. Seems like every OS and programming language in existence uses it. None of them use it exactly the same way it seems.