This command causes a status response to be sent as a reply.
The command may be sent during a file transfer to view the status of the
operation in progress. It may also be sent between file
transfers in which case, the command may include a pathname and
is analogous to the "list" command, except that data shall be
transferred over the control connection.
If no argument is given, the server returns general
status information about the FTP server itself. This
can include current values of all transfer parameters and
the status of connections.