SSH Portforwarding
When having a remote computer (A) in which you’re trying to access the port :3000, you can setup a reverse portforwarding with the following command:
$ ssh -L <port that you want to access locally>:localhost:<port that you want to
connect to> <user>@<ip>
$ ssh -L 3000:localhost:3000 pi@myipaddress
This way, you can access http://localhost:3000 and it is actually communicating with myipaddress:3000.
All securely too!