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...

Status: Obsolete Closed: Dec 2014

Sigh.

are you sure it's Signal? cause i have this problem with my husband too, but it happens with Hangouts as well as with Signal. my best guess is that his android phone, a cheaper LG model, has limited resources and puts some services to sleep...

Yes, because it happens on recent hardware (a 6s) and other messaging systems don't seem to have this issue at all under the same conditions.

Most of the time it would work fine, but quite frequently messages would be sent (have left my device) but not appear on the receiving device for ages, so i can only assume that sometimes the infra couldn't keep up.

Is there no acknowledgement of received messages? That seems somewhat of an oversight over unreliable third-party transports.

Yes, there is.

I used to have the problem but just trying it again now the situation has dramatically improved for me.