If you use one of these port numbers you may run into conflicts with the "well known" application. Ports from 1024 on are freely useable. As an example, you could use port 30443 for SSL VPN if your VPN gateway supports port reassignment and the SSL VPN client (if any) does this as well.
What is SSL VPN and how does it differ from IPSec VPN Oct 15, 2018 How do I configure the SSL-VPN feature for use with Navigate to the SSL VPN | Server Settings page. Click on the Red Bubble for WAN, it should become Green. This indicates that SSL VPN Connections will be allowed on the WAN Zone. Set the SSL VPN Port, and Domain as desired. NOTE: The SSL VPN port will be needed when connecting using Mobile Connect and NetExtender unless the port number is 443 Cookbook | FortiGate / FortiOS 6.0.0 | Fortinet
Nov 22, 2018
Navigate to the SSL VPN | Server Settings page. Click on the Red Bubble for WAN, it should become Green. This indicates that SSL VPN Connections will be allowed on the WAN Zone. Set the SSL VPN Port, and Domain as desired. NOTE: The SSL VPN port will be needed when connecting using Mobile Connect and NetExtender unless the port number is 443
What is SSL VPN? - PureVPN Blog
Version 10 Document version 1.0 – 10.6.6.042 - 24/11/2017 Cyberoam SSL VPN User Guide port-forwarder-cisco-download-ssl-vpn free download May 25, 2020 SSL VPN between DrayOS Router and Vigor3900/2960 | DrayTek