522: No IPv4 address available for PASV. Use EPSV.

Explanation

The client sent a PASV command to the FTP server to establish a data connection. An affirmative PASV reply must include the server's local IPv4 address. The server cannot reply affirmatively to PASV because it has no local IPv4 address for the PASV reply.

Some FTP clients recover automatically from this situation by sending an EPSV, EPRT, or PORT command to establish the data connection.

System action

The server rejects the PASV command. The FTP server processing continues.

User response

If the client recovered from the error by using a different command to establish the data connection, no further action is needed. Otherwise, report the error to the system programmer.

System programmer response

Choose one of these solutions:

Configure the FTP client to use EPSV instead of PASV when establishing a passive data connection.
Configure the client to use PORT instead of PASV to establish a data connection (the client must have an IPv4 address that is reachable from the FTP server).
If the server has an IPv4 address and an IPv6 address, specify the server's IPv4 address when logging in to FTP.

If none of these solutions is feasible, report the error to the provider of the FTP client software.