501: command supported only in Stream mode
Explanation
The LIST or NLST command was entered, but the FTP session was in a mode other than stream mode. The LIST and NLST command are supported only in stream mode.
System action
The LIST or NLST command is rejected.
User response
Issue the MODE S command to change the mode to stream mode, then reissue the LIST or NLST command.
System programmer response
None.