And because you are using VPN server on 127.0.0.1 / any listening port you want ( TCP ) it is no problem to come on wan on 443 TCP ( on any Virtual IP ) and forward to 127.0.0.1 / listening port. ( set on NAT )
This how I configured my server and depend of country/users IP I also come on other ports (443, 4343, 43434… ) that are forwarded to the same server on 127.0.0.1/43434 TCP