How do I test Multiplayer without Internet?

I tested the new Multiplayer chat demo on my LAN, but it works only with Internet connection.

There is a way, but it is like talking to yourself. In the browser add two localhost:50000 pages, so sign up in both and you can chat with yourself or even play with yourself. (note: it is not sufficient or accurate enough though) it's just a personal exprierence

I wanna play with my friends over lan with multiple connected computer (not in localhost) .... also note that, even within the same computer with localhost it wont work without an internet connection.

You need an internet connection because you are using scirra's signaling server which relays info between players.