Example implementation of an FCM App Server using XMPP protocol in C++. If you are looking to build an App Server to serve as a back end for your IOS/Android App, this is what you need. It relies on GIMMM to send/receive messages to/from your mobile application via the Firebase Connection Servers.
Implemented in C++ using QT framework.
Get the server up and running and exchanging messages with your mobile app in under 5 mins! https://github.com/rajeshkhumanthem/GIMMMAPPSERVER/wiki/Quick-Start