Mobile Messaging Push Notifications

The cluster discusses how messaging apps like Signal handle notifications and offline message delivery on mobile devices using push services such as Google FCM/GCM and Apple Push instead of persistent connections to conserve battery and manage connectivity issues.

📉 Falling 0.4x DevOps & Infrastructure
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Keywords

GCM FCM P2P PC XEP MITM SMS ADM NAT GP messages server message phone notifications app client connection push offline

Sample Comments

niklasni1 Aug 11, 2015 View on HN

On mobile you want messages to come through without each app maintaining a connection.

izacus Dec 31, 2016 View on HN

Just like Apple Push or Google FCM. How would that work otherwise if not with an idle connection? :)

jjeaff Mar 10, 2019 View on HN

Signal uses gcm to push to the phone thus waking it so it can download any messages. Not sure about the others though.

miah_ May 31, 2024 View on HN

Not getting messages when I'm offline is a feature.

wmf Feb 3, 2012 View on HN

I guess they don't want the app to hold open connections to every site (some people have solved the C1M problem but some haven't) and they probably want a server to buffer messages when the app is not running. You'd run into these same issues whether the notifications are received by Firefox or a different desktop app.

berdario Feb 4, 2015 View on HN

I assume it's because not every server (most notably: google's) support the XEP for offline messages, and having to always keep a connection to the remote server is mobile/battery-unfriendly.All these newfangled alternatives usually rely on the Google services' push notifications api afaik.

MattJ100 Oct 6, 2025 View on HN

Or push notification support (which is the same, but basically the OS (Android/iOS) is the thing holding an open connection :) )

newjersey Nov 3, 2015 View on HN

It uses Google Cloud Messaging. There needs to be a server in between and I believe GCM is free. Consider a situation where Bobs phone is switched off. Alice sends a message and turns off their phone. Now, Bob turns in their phone. How do we get the message Alice sent to Bob?

GutenYe May 13, 2015 View on HN

How does it manage the offline messages without a server?

eesmith Dec 5, 2017 View on HN

Couldn't the intermediate conversation be stored and sent when there's connectivity?