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Comment by tjohns | Hacker News Reader

GCM/FCM will delay low priority notifications, in order to batch as many together as possible.

On top of that, the cell networks don't allow keeping a socket open for more than a few minutes without sending keepalive packets. Unlike on desktop, keeping a socket open isn't "free" on mobile.

Waking up the cell radio has a significant penalty on battery life.

(And yes, Android batches up process wakeups as well. See the docs on "Doze Mode": https://developer.android.com/training/monitoring-device-sta...)

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So you just batch the keepalives, like the old Nokias were doing. Reaching 1 month long battery lifes with Jabber on.

Absolutely no difference 1 having to send 1 keepalive every 5 minutes than 30.

This is just a subversion of basic networking in order to centralize everything through a single provider and as usual the users are trained to see it as necessary without questioning it.

> On top of that, the cell networks don't allow keeping a socket open for more than a few minutes without sending keepalive packets. Unlike on desktop, keeping a socket open isn't "free" on mobile.

You are wrong. Cell networks don't prevent you from keeping a socket open for however long you want. For how to keep your sockets alive, see https://developer.android.com/reference/android/net/SocketKe...

Keepalive across cells are not universally available. Most mobile networks renew your IP at each handover.

That method just instructs the OS to send keepalive packets on a system thread.

It saves some CPU power by letting your process sleep, but still requires waking the cell radio up periodically.

The implementation can be found here: https://github.com/aosp-mirror/platform_frameworks_base/blob...

That's right. And it should work as advertised in the documentation. Anyway, I was responding to the "cell networks don't allow" part of your comment. Cell networks don't have a say in what I do at IP/TCP layer.

They literally said that cell networks don't allow it without the keep alive. You quoted it and said they were wrong because... you can use a keep alive. I'm confused as to what you're correcting.

There are collaborations between mobile network providers and push notification providers to get these sockets special-cased. I.e., they won't need keep-alive at any regular interval. So the radio can actually get layer-1 pings (like, when you're called, or get an SMS) for push notifications.

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