Port 7902 not mentioned in documentation

Technical Discussion
#1

https://docs.symbolplatform.com/guides/network/using-symbol-bootstrap.html says:

Make sure that the server’s host is accessible from the internet and that **the following ports are open and available**:

* Port `7900` is used by catapult-server to communicate between nodes.
* Port `3000` is used by the REST Gateway to expose the endpoints to interact with the node.

I see symbol-bootstrap configures port 7902 too.
Symbol whitepaper says this is for notification subscriptions by clients.
Is it used by existing wallets?
Should we open it at firewall level?

#2

I think 7902 is used only to communicate internally between containers and not outside VPS so you don’t need open it.