xmpp - How to find out if a given resource of a JID is online/offline with smack -

how can tell juliet@verona.it/balkony (full jid!) online/still available smack?

subscribe juliet@verona.it's presence, go online sending own presence in, , see if presence stanza back. querying presence doesn't make sense; think of stepping flow of juliet's presence @ point in time.