What ports should ideally be open?

Question

System administration

I decided to look at open ports through nmap on my vps. I see, for example:

3306/tcp open mysql

Here I do not quite know if the mysql port should be open.
Because, for example, with the same nmap I send a request to another server, and there mysql is not shown at all in the list of ports (although it is on that server). Only open ports 80 and 443 are shown there.
The question is: which ports should ideally be open? if i close the mysql port i can only connect to it from my VPS? From my IP address, I can no longer connect to the database, do I understand correctly?

Answer 1

Outside - should not!
Close the binder on the external interface!
Leave the binding only on the "local loop" (localloop) interface: localhost/127.0.01

Answer 2

Here I do not quite know if the mysql port should be open.

Outside - should not. Only the ports that serve the services running on this server should stick out.

Answer 3

What ports should ideally be open?

Everything you need and closed everything you don't need.

Here I don't quite know if the mysql port should be open

So you obviously do not have enough qualifications to configure the firewall. This task must be performed by a system administrator.