What are the right parameters for xmpp-connection (spring integration) to make it work with google gcm?

I want to setup spring-integration-xmpp on my spring app to make it receive upstream messages from android devices. I can already send messages to the android device using http but I cannot set up the xmpp-connection bean so it gives me:

failed to connect to gcm-preprod.googleapis.com; nested exception is Connection failed. No response from server.:

This is my spring integration configuration:

  <int:channel id="gcmOutboundNotificationChannel"/>

  <int-xmpp:xmpp-connection
    id="xmppConnection"
    user="${tracker.server.app.id}@gcm.googleapis.com"
    password="${tracker.auth.key}"
    host="gcm-preprod.googleapis.com"
    port="5236"
    subscription-mode="accept_all"/>

  <int-xmpp:outbound-channel-adapter
    id="gcmOutboundAdapter"
    xmpp-connection="xmppConnection"
    channel="gcmOutboundNotificationChannel"/>

tracker.server.app.id is a 12 digit number and tracker.auth.key is like AIzaSyBdfZ4oBaVuu07sjW5e9DnogeUF6NV**** (I put in the asterisks).

What am I missing?