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.
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