Do you have IPv6 in your home network ? Many devices (such as all the Samsung one) stop responding to ICMPv6 packets when in sleep mode (which completely breaks long-running TCP connections over v6), supposedly to save power. This breaks push notifications of every apps using GCM, but there is no way to disable IPv6 without root, and no way to only use GCM over IPv4. I find it mind-blowing that this issue has been known for 3 years and nothing has been done to fix it...

Issue from 2012: https://code.google.com/p/android/issues/detail?id=32662

Thread starting in 2013 on Samsung dev board: http://developer.samsung.com/forum/board/thread/view.do?boar...