FTP Server: Unable to list directory content with Error 425


Almost every time the error is “425 Can’t open data connection” and it is when the FTP Server tries to enter Passive Mode. This is 100% a firewall issue. You might have port 21 open already but the firewall is blocking the default port used for passive mode.

At this point you have two options:

  1. Find the default port used for Passive mode and open that port in the firewall

  2. Better FTP Server allow you to change the port used for passive mode so go ahead and change it to the port you’d like. Make sure the port is not being used by other programs (use netstat -a) and make sure to open the port in the firewall

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