FTP Commands: MDTM, MKD, MODE, NOOP, SSCN, SCRC

The MDTM command implemented by FTP Voyager and Serv-U is used to preserve a file’s original date and time information after file transfer.

Traditionally, when a file is uploaded to an FTP server, the date or time of the file is set to the transfer date or time. Using MDTM, FTP Voyager can inform supporting FTP servers of the proper date/time to use for the file. The format of the command is MDTM YYYYMMDDHHMMSS, where:

• YYYY – the 4-digit year
• MM – the 2-digit month
• DD – the 2-digit day of the month
• HH – the hour in 24-hour format
• MM – the minute
• SS – the seconds

Common responses:

• 421
• 500, 501, 502, 530, 550

This command causes the directory specified in the pathname to be created on the server. If the specified directory is a relative directory, it is created in the client’s current working directory.

Common responses:

• 257
• 421
• 500, 501, 502, 530, 550

This command changes the transfer mode. The argument is a single Telnet character code specifying the data transfer modes described in the Section on Transmission Modes.

The default transfer mode is Stream. Mode Z (commonly referred to as “on-the-fly” compression) is defined in an IETF draft.

Common responses:

• 421
• 500, 501, 504, 530

The NOOP command does not cause the server to perform any action beyond acknowledging the receipt of the command. This command can be issued to the server to prevent the client from being automatically disconnected for being idle. It can also prevent modern routers/firewalls from closing a connection that it perceives as being idle as well.

Common responses:

• 421
• 500

The SSCN command allows the client to tell the server to use a secured connection when transferring files directly between servers via FXP. Traditionally, FXP transfers are sent in an unsecured format, with data and credentials sent in the clear. Using the SSCN command allows the servers involved in the transfer to secure credentials and the files transferred.

Common responses:

• 501, 533

The XCRC hash command asks the server to perform a cyclic redundancy check using the CRC-32 algorithm on the specified file. If the XCRC command is supported, the server will respond with the result of the calculation. FTP clients can use this command to verify that the file was transferred without corruption by comparing the server’s response with its own calculation.

Common responses:

• 250
• 500, 502, 530, 550

• LIST FTP command
• RMD FTP command
• PASS FTP command
• TYPE FTP command
• RMDA FTP command
• XCWD FTP command
• SYST FTP command