I have an app that sends/receive data via HTTP POST, and communicates with PHP/SQL on the backend.
I however wanted to integrate GCM to I can tell the app to "check for an update" to query the server. I wanted to sell the app, and the user has to run the server themselves (the PHP backend). However, I assume I can't publicly list my Google API key. Am I correct in saying that? That throws GCM out the window.
I'm new to sockets, but can I create a TCP connection between the device and server, and send requests back and forth. Or does there need to be two sockets, one to send request, and one to listen?