Can't establish connection to Google's Firebase XMPP server

[vmarkushin]

For convenience, the problem is described here: https://stackoverflow.com/questions/52777629/how-to-establish-connection-to-google-firebase-xmpp-server
Firebase support said: "Looking at the logs, it seems that this is more of a library or setup issue rather than FCM itself."

[Kev]

Hi - I don't know anything about Firebase, but what is getting returned on your connection isn't what an XMPP server would return (it would return XML), even on an error, so I don't think I can sensibly help with this.