[Andrew_nenakhov]

Format of APNS messages is just a payload. The information about APNS being based on XMPP was widely available on developer.apple.com and was often mentioned in developer sessions in 2010..12 when I was actively following it.

The current absence of direct XMPP mentions on Apple Deveoper website might mean that they consider their internal technology not important for developers, or it might mean that Apple had changed the protocol for some reason (they could have opted to use some binary protocol, for example), but claiming that push notifications work on iOS devices by polling servers is beyond ridiculous. VoIP pushes arrive in ~1 second. Such response times would require 40000 poll requests/day or more

[icedchai]

I never claimed APNS worked by polling. I was developing iOS apps in the 2010-2012 time frame and never saw a mention of XMPP. I simply don't believe they are using it. They must have their own proprietary solution.

[Andrew_nenakhov]

> I never claimed APNS worked by polling.

I was referring to earlier comments by nicolas314, sorry if it wasn't clear.

> I was developing iOS apps in the 2010-2012 time frame and never saw a mention of XMPP

I might have been more attentive to these details because XMPP was relevant for my projects. Anyway, Apple definitely does use port 5223 [1][2] for push notifications. What protocol is known to use this port?

Speaking of proprietary, it is very likely that they have modified it (by stripping it down, mostly). Many XMPP features are excessive or inefficent for push notifications, but core functions - message routing and persistent TCP connection are extremely well suited for serving several billion devices.

[1] https://support.apple.com/en-us/HT203609

[2] https://support.apple.com/en-us/HT210060