In order to make FTP workable without needless error messages, the following minimum implementation is required for all servers:
TYPE - ASCII Non-print MODE - Stream STRUCTURE - File, Record COMMANDS - USER, QUIT, PORT, TYPE, MODE, STRU, for the default values RETR, STOR, NOOP.
The default values for transfer parameters are:
TYPE - ASCII Non-print MODE - Stream STRU - File
All hosts must accept the above as the standard defaults.