Own PUSH server for Android without node.js, any solutions?

Question

PHP

Hello.
We make applications for local use. There was a need to send messages to applications ala GCM, only the problem is that the application does not have access to the external network, and should not have, so the implementation from GOOGLE is not suitable. I would like to know if there are ready-made implementations of PUSH servers for local use?
We are not friends with Node.js at the very least, I would like to find PHP / Java solutions.
Thank you in advance!

Answer 1

bash + curl, no problem.
https://packagist.org/packages/endroid/gcm - I use this on some projects. Java has an official client.