Ahoy!
I play today with making a real time collaborative app and recalled using last time for such purpose:
http://faye.jcoglan.com/
"Faye is a publish-subscribe messaging system based on the Bayeux protocol. It provides message servers for Node.js and Ruby, and clients for use on the server and in all major web browsers."
from:
http://svn.cometd.com/trunk/bayeux/bayeux.html
"Bayeux Protocol -- Bayeux 1.0.0
Bayeux is a protocol for transporting asynchronous messages (primarily over HTTP), with low latency between a web server and web clients."
Now noticing familiar name of its author: jcoglan :)
Maybe worth investigating for messaging?
Cheers!