Can Google cloud messaging deliver a “zero byte load” notification to a phone that can receive voice calls and SMS, but for some reason does not have a data connection at the moment?
By "zero byte" I mean that the phone will know that a GCM notification that did not have a payload was sent to it by a specific sender and could conceal its intention to do so.
Real world example: a burglar alarm is triggered and two push messages are sent to the homeowner - a message with a zero byte, the meaning of which is implied entirely because it was sent at all, implies that something bad is happening "and can (presumably) be delivered , even if the data connection is blocked or unavailable, because it (presumably) moves along the same transport level that is used for SMS, and a longer push notification sent after a few seconds with additional meta-information about the situation, this can only work in that If at the moment there is the possibility of connecting to the data (so that the phone can be notified and receive a payload from the server after establishing a normal data transfer session).
I read Google docs, but it seems they deliberately leaned back to say nothing about the physical transport layer of GCM.
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