An acronym for eXtensible Messaging and Presence Protocol This is the generalized XML streaming protocol that underlies Jabber (and the newly hyped 'Google Wave').
See RFC 3920 [L1 ], RFC 3921 [L2 ] and http://www.xmpp.org/
RLH 2009-06-01: Does Tcl have anything library wise that talks xmpp?
schlenk 2009-06-04: Not nicely package as far as i know, but tkchat, tkabber and the coccinella all speak xmpp and should have the needed libs included.
DKF: XMPP can also be used as a transport protocol for SOAP, which is helpful for when you have long-lived webservice communications between two parties (especially when one party doesn't want to open incoming ports in their firewall).