Will Web notifications work in a closed network?

Question

PHP

There is crm which works in a local area network without access to the Internet. Is it possible to implement Web notification? I had no experience with them, and in order not to go through heaps of documentation, I decided to ask.
In particular, as I understand it, there are some keys that the browser probably checks in some certification authorities. Perhaps stupidity, this is after a cursory acquaintance.
Well, the most terrible question is whether it will be possible to organize a message server in php? Without node.js etc. There is a difficulty with the additional installation of what was not originally intended.

Answer 1

No. Google servers are involved

Answer 2

Will (but not Web notification). redis+node+socket.io You can
do it without node.js , but it's better not to.