Can I use another port other than 443 for HTTPS/SSL communication?

The port number is not “magic”, you can use any port from 1-65535 you like. There are only 2 conditions:

1. Both the server and the client have to (agree to) use the same port number.
2. Ports in the range 1-1023 are “well known ports” which are assigned worldwide to specific applications or protocols. If you use one of these port numbers, you may run into conflicts with the “well known” applications. 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. If you access SSL VPN via web portal, you can add the custom port number in the URL like this: “https://mysslvpnserver.com:30443”.
Beware that public internet feeds (hotels, hotspots) often block high ports > 1024.