Update 9/22/2012: Please try JohnnySheffield new plugin at http://www.scirra.com/forum/plugin-zack0wack0s-socketio-mod_topic56503.html. He updated the plugin to work with minify and other goodness. Thank you.
Based on the work of Zack0Wack0, I was able to modify a little bit his excellent socket.io plugin and created a small top-down shooter game.
To download the demo and the modified version of the socket.io plugin, please go here and download the "socket-io-mod.zip" file.
Before you can use the plugin and the example, please install node.js and socket.io as Zack0Wack0 explained in his post. If you are using Windows, I strongly suggest that you open the CMD, cd to C:\node_modules (create that folder is not present) and run the "npm install socket.io" from there. It seems that Node.js has "C:\node_modules" hardcoded as one of the paths to find installed modules.
Once you install node.js and socket.io, you can CD into the folder that contains example_server.js and type "node example_server.js" in the commnad prompt. The server will run listening for connections on port 8099.
Open the capx and run it, make sure the "ChooseServer" layout is the 1st to run.
For server address you can enter the IP of the computer that is running the server, if it is the same computer, you can enter 127.0.0.1.
Enter 8099 in the server port and click Connect.
If you run the capx in another computer, make sure you enter the appropriate IP address of the computer running the node.js server.
You can also try to run two separate instances of the game in the same computer by just opening two broser windows and going to the address where you game is (default for preview localhost:5000).
I have only tested it in Chrome and Windows. Also, if you want to export the project, avoid checking "minify" for some reason I can't get it working with that, I think Zack0Wack0had the same problem.
You can watch a video of the sample game in a LAN here
I wrote a new post in my blog on how the multiplayer demo works in Construct2:
I also uploaded a new video showing an iPad connecting to the game: