How we can know the chat session of Xmpp user closed?

Hi All,

I am trying to maintain a chat context for two clients, in those one supports chat mode informal ,
other does not, so i would like to maintain chat context in my server and get response on same thread id from other client .To make informal chat explicitly. Now is there any way to find the other client has closed chat session,
or when he/she goes off-line. I dont want to made presence and message modules tightly coupled.

how can i know the other user is offline in message module? any info query or some query ? I tried last query not succeeded.

Regards,
GVK