Directory listing from FileZilla Server fail with 425 Can't open data connection for transfer of "..."

Solution 1:

Command: PASV
Reply: 227 Entering Passive Mode (XX,XX,XX,XXX,166,216)
Command: MLSD
Reply: 425 Can't open data connection for transfer of "/"

The data connection port on your FTP server is not accessible.

The port number for this specific connection was 42712 (=166*256+216). But in general, there's a port range. So that whole port range needs to be made accessible.

Check all firewalls (both internal on the FTP server machine and external) and NATs on the way between your client and the server. They all need to allow and correctly route the connections to the ports in the data connection port range.

For details, see

• Setting up and testing FileZilla Server
• Or my generic article network configuration required by FTP protocol.