title: Check for Online status of Roster Item using AGSXMPP
body: <p>I am using AGSXMPP Library with C#. Everything works fine except <code>OnPresence</code> event is not firing when a GTalk user is disconnected from the Internet and the user's status remains as Online. Is there is a way to check for status of the <code>RosterItems</code> periodically?</p>