Google Talk is an XMPP  (aka. Jabber) based Instant Messaging IM application that is tied in with Google's e-mail handling service Google Mail. Google provide a client that can do the usual IM activities (messaging, chat and group chat) and also does voice and video links using their Jingle extension  to the XMPP protocols.As XMPP is an open RFC derived from Jabber and Google have hooked their servers into the Jabber network we can access Google Talk users from outside servers and also use alternative clients. Specifically Tcl/Tk clients.tkabberTo connect to a Google Talk account of [email protected] using tkabber we must set the username to the part before the @ (ie: an.other) and the server to the part following the @ (thus: gmail.com). However Google Talk actually operates on the talk.google.com servers so on the second page of the login dialog we must check the 'Explicitly set host and port' checkbox and set the server on this page to talk.google.com and the port to 5222. On the authentication tab you MUST check the 'Allow plaintext authentication mechanisms' checkbox. Google Talk only provides X-GOOGLE-TOKEN and PLAIN SASL mechanisms for authentication. Tkabber doesn't understand the first so we must do PLAIN authentication which is provided once we set up the TLS secure channel. Which leads us to the SSL page. Ensure that the STARTTLS radio button is set. Once the above is done you should be able to connect to Google Talk using Tkabber.PT 19-Apr-2006: The lastest tkabber-pat.kit  supports the special Google authentication mechanism so it should now work seamlessly with Google Talk accounts. It is no longer necessary to use plaintext authentication unless you have trouble with secure web access. Support for the X-GOOGLE-TOKEN SASL mechanism is now part of tcllib.
Sly 2007-12-10: Can't connect to Google jabber server in any way.In the best case, I get the error message "Server provided mechanism X-GOOGLE-TOKEN. It is forbidden".Can't connect to Livejournal jabber server either.