FTP reply code 215 is the response to the SYST command, which asks the server to identify its operating system. The response follows the format specified in RFC 959 and typically contains the system name from the IANA operating system names list. Common responses include 'UNIX Type: L8' (most Linux/BSD servers), 'Windows_NT' (IIS FTP), and 'VMS' (OpenVMS). FTP clients use this information to determine directory listing format (UNIX ls format vs. Windows DIR format), line ending conventions, and filename case sensitivity.
The client sent SYST to identify the server's operating system. FTP clients issue this automatically after login to configure their directory listing parser and filename handling for the server's OS.
If directory listings appear garbled, the FTP client may be using the wrong parser. Send SYST to see if the server identifies as UNIX, Windows, or another system, and configure your client accordingly.
curl -v ftp://ftp.example.com/ -Q 'SYST'
If the server supports MLST/MLSD (check via FEAT), use these instead of LIST. MLSD returns directory listings in a standardized machine-readable format that does not depend on the operating system.