As has been mentioned before on this blog, OpenSRF relies on Jabber for it’s communication layer. Jabber is an instant messaging service much like AIM, Yahoo messenger, and the like. The advantage of Jabber, of course, is that it’s an open spec (see xmpp.org) and there are a number of open source server implementations, allowing us to run servers localy and write our own server code if we feel so inclined.
Like most chat frameworks, a Jabber client is distinguished by its username on the network. So a unique Jabber “account” would consist of something like bill@gapines.org. Jabber also adds an additional component which is called the “resource”. This allows a single account to have multiple open connections to a jabber server. A full client login would be something like bill@gapines.org/home, bill@gapines.org/work, etc. A single user may be logged into a given server as many times as they want so long as the resources are unique for each connection.