private void probePresence(JID probee) {
        final PresenceManager presenceManager = XMPPServer.getInstance().getPresenceManager();
        for (ClientSession session : SessionManager.getInstance().getSessions(username)) {
            presenceManager.probePresence(session.getAddress(), probee);
        }
    }
Sends a presence probe to the probee for each connected resource of this user.
xmppserver/src/main/java/org/jivesoftware/openfire/roster/Roster.java