Thursday, 19 May 2016
Google Android GCM delay.
GCM instant notification is not guaranteed:
GCM will usually deliver messages immediately after they are sent. However, this might not always be possible.
The GCM framework part on the client phone use a TCP connection on the port 5228. This connection its used for push notifications, but this connection can go timeout (tcp idle timeout). Some wifi routers kills inactive connections after x minutes.