FTPS implicit TLS/SSL error

Question

I am using FTP over implicit SSL to upload some files. I encountered the following error message

[Command]  PWD
[Response]  257 "/" is current directory.
[Command]  PWD
[Response]  257 "/" is current directory.
[Command]  TYPE A
[Response]  200 Type set to A
[Command]  PWD
[Response]  257 "/" is current directory.
[Command]  PASV
[Response]  227 Entering Passive Mode (10,0,0,19,195,113)
[Command]  LIST -aL
[Response]  521 PROT P required
[Command]  PWD
[Response]  257 "/" is current directory.
[Command]  PASV
[Response]  227 Entering Passive Mode (10,0,0,19,195,114)
[Command]  LIST -aL
[Response]  521 PROT P required
[Status] Failed::FTP protocol error. 521 PROT P required.

May I know what is this error message "521 PROT P required" saying?

Thanks

Answer 1

type the following: set ftp:ssl-protect-data true

Answer 2

Before starting a data transfer (e.g. creating a new data connection outside the control connection to transfer files or listing) you have to specify the protection level using the PROT command. The main protection levels are P for protected (e.g. SSL encryption) or C for clear (no encryption). The server complains, because you don't specify a protection level and so it does not know how you want to get your data.

The PROT command must be implemented and used by all ftps clients.