Using a custom port is not the issue. We test WebDAV using a dockerized NextCloud installation and a Synolody NAS server. By nature of this testing methodology, the former always uses a custom port (6901), while the latter uses a standard port (443). This way we check WebDAV with both custom and standard ports alike.
Besides, you can see in the log that the new, custom, port is used just fine, e.g.:
DEBUG |20230925 09:02:54|Absolute WebDav URL: https://webdav.imrus.hu:8443/20230925/
The actual problem is that server refuses the connection when we try to list the folder's contents. That's a problem with the WebDAV server or your host, not our code.
Since you tried with a different software from your computer and the WebDAV upload works it means that the WebDAV server itself is working fine. This leaves us with your host. Can you please ask them to allow HTTPS connections to webdav.imrus.hu over port 8443 through their firewall / proxy?
Nicholas K. Dionysopoulos
Lead Developer and Director
🇬🇷Greek: native 🇬🇧English: excellent 🇫🇷French: basic • 🕐 My time zone is Europe / Athens
Please keep in mind my timezone and cultural differences when reading my replies. Thank you!