I have developed one Android app for the company which has Push Notification(GCM) as well.
When they send the notification and that time if the device is connected in their wifi network then notification doesn't come but if the device is connected to mobile network (3G/4G) then it receives the notification.
Their system admin might have blocked that web address but nobody knows exactly which address.
So, I just wanted to know which Google API gets called when notification arrives so that I can inform their System Administrator to unblock that web site/web address