I’'m not sure I completely understand your issue. Is this a Jive Messenger question or a Smack question?
If this is a Messenger question then your chat service should not have the same XMPPAddress as the main server. For example, if your server’'s address is “localhost” then your chat service must be something different than “localhost”. A common address could be “chat.localhost”.
Now I got your question. The reason for that is that Chat does not make use of the Chat service in the server whilst GroupChat does. Maybe the name of the class Chat can give you the wrong idea. The Chat class only sends regular messages between two parties. On the other hand, GroupChat generates a virtual room on the server and therefore the chat service is used.