Yes, it is possible.
The XMPP Service in GAE also allows you to enable the xmpp_subscribe
inbound service. By enabling that in your appengine-web.xml file, you will be able to get the following notifications at the endpoints given below:
- POSTs to /_ah/xmpp/subscription/subscribe/ signal that the user wishes to subscribe to the application's presence.
- POSTs to /_ah/xmpp/subscription/subscribed/ signal that the user has allowed the application to receive its presence.
- POSTs to /_ah/xmpp/subscription/unsubscribe/ signal that the user is unsubscribing from the application's presence.
- POSTs to /_ah/xmpp/subscription/unsubscribed/ signal that the user has denied the application's subscription request, or cancelled a previously granted subscription.
I have taken the above points from the official documentation. Please refer to the https://developers.google.com/appengine/docs/java/xmpp/overview#Handling_Subscriptions for more details.