Zend certified PHP/Magento developer

placing the REST server inside the VPN network so that only VPN clients can access it

I learned how to deploy REST server and VPN server separately but I don’t have enough knowledge to make them work together. So my questions are the following:

  1. how to force the REST server to listen to the address in the VPN network?
  2. how to add DNS to this system?
  3. Will Docker be useful? if so, how to do all of the above in Docker?

operating system – Ubuntu 22.04. I want to get an answer without being tied to a specific technology implementation (vpn, rest, etc.) in order to have an idea about the setting the above in general