This library aims to make writing XMPP clients (in particular bots) easy and fun. Here is a small example:

 import XMPP
 import Network
 
 -- The bot's JID is "bot@example.com"
 botUsername = "bot"
 botServer = "example.com"
 botPassword = "secret"
 
 main :: IO ()
 main = withSocketsDo $
   do
     -- Connect to server...
     c <- openStream botServer
     getStreamStart c
 
     runXMPP c $ do
       -- ...authenticate...
       startAuth botUsername botServer botPassword
       sendPresence
       -- ...and do something.
       run
 
 run :: XMPP ()
 run = do
   -- Wait for an incoming message...
   msg <- waitForStanza (isChat `conj` hasBody)
   let sender = maybe "" id (getAttr "from" msg)
       len = length $ maybe "" id (getMessageBody msg)
   -- ...answer...
   sendMessage sender ("Your message was "++(show len)++" characters long.")
   -- ...and repeat.
   run

XMPP is a protocol for streaming XML also known as Jabber. It is described in RFCs 3920 and 3921, and in a series of XMPP Extension Protocols (XEPs). All of this can be found at http://www.xmpp.org.

For a larger example, see werewolf.