I am currently working on a port of the xiff library to AS3. This library was originally coded by Sean Voisen http://www.voisen.org/.
If you want any info about the current library go to http://www.jivesoftware.org. This library is protected by the "GNU LESSER GENERAL PUBLIC LICENSE, thus you will have access to all the source when it is complete. I will be posting a flex demo soon at http://www.velloff.com.
This library can easily be used to built chat clients among other xml socket based communication. It is a cheap alternative to Flash Media Server as there are a number of open source servers out there that support XMPP. Jive Software's Wildfire supports Flash player's socket nuances right out of the box, and is a breeze to set up.