FTP Reply Status Code
First digit of status code indicates type of
reply:
‘1’:  Positive Preliminary Reply  (got it, but wait).
‘2’:  Positive Completion Reply (success).
‘3’:  Positive Intermediate Reply (waiting for more
information).
‘4’:  Transient Negative Completion (error - try
again).
‘5’:  Permanent Negative Reply (error - can’t do).