added an echo client example for the new proposed api

Examples/EchoClient.hs

@@ -0,0 +1,63 @@
+{-
+
+Copyright © 2010-2012 Jon Kristensen.
+
+This file (EchoClient.hs) illustrates how to connect, authenticate,
+set a simple presence, receive message stanzas, and echo them back to
+whoever is sending them, using Pontarius. The contents of this file
+may be used freely, as if it is in the public domain.
+
+-}
+
+
+module Examples.EchoClient () where
+
+import Network.XMPP
+
+
+-- Server and authentication details.
+
+hostName = "nejla.com"
+portNumber = 5222
+userName = "test"
+password = ""
+
+
+-- Start an XMPP session with the default settings, open the streams
+-- to the XMPP server, authenticate, send a simple presence, and start
+-- the `echo' XMPP thread.
+
+main :: IO ()
+
+main = session default $ do
+  liftIO $ putStrLn "Welcome to the Pontarius EchoClient example!"
+  openStreamsResult <- openStreams "nejla.com"
+  case openStreamsResult of
+    Nothing -> do
+      liftIO $ putStrLn "Streams opened, now authenticating!"
+      authenticateResult <- authenticate userName password Nothing
+      case authenticateResult of
+        Right _ -> do -- Ignore XMPP address
+          liftIO $ putStrLn "Authenticating, now sending presence!"
+          sendPresence Nothing Nothing [] Nothing -- Simple presence
+          liftIO $ putStrLn "Echoing..."
+          fork echo
+        Left error -> liftIO $ putStrLn "Error: " ++ $ show exception
+    Just error -> liftIO $ putStrLn "Error: " ++ $ show exception
+
+
+-- Pull message stanzas, verify that they originate from a `full' XMPP
+-- address, and, if so, `echo' the message back.
+
+echo :: XMPPThread () -- TODO: XMPP ()? XMPP?
+
+echo = forever $ do
+  result <- pullMessage	
+  case result of
+    Right message ->
+      if messageFrom message /= Nothing && isFull $ messageFrom message
+      then do
+        sendMessage (messageFrom message) (messageType message) Nothing []
+        liftIO $ putStrLn "Message echoed!"
+      else liftIO $ putStrLn "Message sender is not set or is bare!"
+    Left exception -> liftIO $ putStrLn "Error: " ++ $ show exception