Answer by Matija Nalis for How do I port forward if the public/external IP is shared on both my computers?

You can only forward port to one IP at a time

Your laptop has one internal IP, and your main computer another internal IP. Router cannot magically choose to which one of those to forward port 443. You must specify one or the other.

What you could do:

1. Forward port 4431 to one computer, and 4432 to another, and then let the client choose which one it wants by specifying https://name.example.com:4331/ for example

2. Make your laptop and main computer have same IP, but then there can only be one turned on at the same time - if you want to use laptop, you must first turn off desktop, and vice versa. But forwarding will then always go to the powered on computer

3. Floating IP. Have your laptop and main computer have different internal IPs, and make router forward to third internal IP - which you would put up as additional address to either laptop or desktop (but again, only of of them at the time). Advantage over (2) is that you can use both computers for other things; disadvantage is it is more work (unless you manage to script it)

UPDATE if you only want forwarding to your laptop to work, and you've removed forwarding to your main computer (ALL forwardning, not just port forwading - for example, removing main computer as DMZ), than it might be local linux firewall. Try (as root)

iptables -F INPUT; iptables -P INPUT ACCEPT