FTP Commands: QUIT, USER, ABOR, ACCT, SYST, XDEL

This command ends a USER session and if file transfer is not in progress, the server closes the control connection. If file transfer is in progress, the connection will remain open so it can receive the response from the data transfer before the server closes it.

Note: An unexpected close on the control connection will cause the server to effectively respond as though an abort ( ABOR ) and a logout ( QUIT ) were issued.

Common responses:

• 221
• 500

USER is followed by a text string identifying the user. The user identification is that which is required by the server for access to its file system. This command will normally be the first command transmitted by the user after the control connections are made. This command is usually followed by the PASS (Password) command.

Common responses:

• 230, 232
• 331, 332, 336
• 421
• 500, 501, 530

The ABOR command can be issued by the client to abort the previous FTP command. If the previous FTP command is still in progress or has already completed, the server will terminate its execution and close any associated data connection. This command does not cause the connection to close.

Common responses:

• 226
• 421
• 500, 501, 502

The ACCT command is used to provide an account name to the server. The account is not necessarily related to the USER . A client may log in using their username and password, however, an account may be required for specific access to server resources.

Common responses:

• 202, 230
• 421
• 500, 502, 503, 550

A client can issue this command to the server to determine the operating system running on the server. Not all server responses are accurate in this regard, however, as some servers respond with the system they emulate or may not respond at all due to potential security risks.

Common responses:

• 215
• 421
• 500, 501, 502

The XDEL deletes the specified file on the server, and is a duplicate of the DEL command. It is implemented because some firewalls assume that all FTP characters must be 4 characters in length.

Common responses:

• 250
• 501, 550

• LIST FTP command
• PORT FTP command
• REST FTP command
• SITE FTP command
• STAT FTP command
• TYPE FTP command
• MODE FTP command
• RNTO FTP command