Don't need a spare public IP address at all, just an existing public IP and port forward at least TCP 44000 to the internal IP of the 5000 (also 443 for the admin software/web portal access, and possibly 22 for the SSH shell, but neither is really necessary). Just make sure in System-IP Settings you change the System NAT IP Address to the public IP address so the system handles the firewalls NAT correctly. The actual port numbers used are defined in the system, so if 44000, 443, or 22 is used for something else, you can change them.