As I said, domain or subdomain point to IP address (not with port number)View attachment 154094
as you see i am not able to put the port. if i put the port it is not redirected correctly.
so the server also need to run on port 80 or 443 else it wont get the call when someone puts the url in the browser.
domain -> IP
Port 80 is the default port for http web server for serving web page (html or php).
Meaning if we don't start a web server, the VPS is still/already pointed with the domain you set the A record and other services with other port number can already run such as SSH, FTP service.