Seems like a firewall issue. If you have detailed logs in your ftp client, maybe it will show you which port it tries to connect to get the directory listing. If ftp connection tracking is working correctly on the firewall you go through it should be ok. But if you use non standard ftp command ports (other than 21), or use encrypted ftp command connection (FTPS), the connection tracking "cannot see" which ports to dynamically open for ftp data connections.

If it is possible, consider migrating to SFTP/SCP instead of regular FTP, its more secure and more firewall friendly :-)

Hi David Vincze

Thanks for your help

FileZilla is a great program to try as it provides details of the client/ftp conversation.

The FTP server may not have permissions to the list the directory but only serve specific files. Blind repositories are not unusual.

See what FileZilla can see.

Dear researchers, I thank you all for your help. I was able to connect to the server folders with FTPS format according to Mr. David Vincze's advice.