File Transfer Protocol, or FTP, is a system for transfering files from one computer to another. The files can have any form; text files, images, compressed files, raw data, etc.

FTP is a client-server system. A person who wants to transfer files runs a program called the FTP client and connects to an FTP server somewhere on the internet or an intranet. The server asks for identification in the form of a username and usually a password. The person supplies these to the client which passes them along to the server. The username and password must be obtained independently of the FTP protocol, usually in the form an account assigned to that person, except that many FTP servers provide a form of public access to the username anonymous for which any password is accepted.

Once connected, the person can navigate the file system the server makes available, retrieve directory listings and files, send files to the server, create directoies, rename or delete files, and possibly perform other operations. However, the files which the server makes available and the operations it permits are typically dependent on the account used to connect to FTP. The anonymous account typically has the least permissions, usually limited to retriving directory listings and files and possibly sending files to one directory set aside for uploads.

The protocol is defined by RFC 959.

Common Commands

  • ABOR - abort a file transfer
  • CWD - change working directory
  • DELE - delete a remote file
  • LIST - list remote files
  • MDTM - return the modification time of a file
  • MKD - make a remote directory
  • NLST - name list of remote directory
  • PASS - send password
  • PASV - enter passive mode
  • PORT - open a data port
  • PWD - print working directory
  • QUIT - terminate the connection
  • RETR - retrieve a remote file
  • RMD - remove a remote directory
  • RNFR - rename from
  • RNTO - rename to
  • SITE - site-specific commands
  • SIZE - return the size of a file
  • STOR - store a file on the remote host
  • TYPE - set transfer type
  • USER - send username
Uncommon Commands
  • ACCT - send account information
  • APPE - append to a remote file
  • CDUP - CWD to the parent of the current directory
  • HELP - return help on using the server
  • MODE - set transfer mode
  • NOOP - do nothing, common keep alive command(thanks sharq)
  • REIN - reinitialize the connection
  • STAT - return server status
  • STOU - store a file uniquely
  • STRU - set file transfer structure
  • SYST - return system type

ABOR
Syntax: ABOR
Aborts a file transfer currently in progress.

ACCT*
Syntax: ACCT account-info
This command is used to send account information on systems that require it. Typically sent after a PASS command.

ALLO
Syntax: ALLO size R max-record-size
Allocates sufficient storage space to receive a file. If the maximum size of a record also needs to be known, that is sent as a second numeric parameter following a space, the capital letter "R", and another space.

APPE
Syntax: APPE remote-filename
Append data to the end of a file on the remote host. If the file does not already exist, it is created. This command must be preceded by a PORT or PASV command so that the server knows where to receive data from.

CDUP
Syntax: CDUP
Makes the parent of the current directory be the current directory.

CWD
Syntax: CWD remote-directory
Makes the given directory be the current directory on the remote host.

DELE
Syntax: DELE remote-filename
Deletes the given file on the remote host.

HELP
Syntax: HELP command
If a command is given, returns help on that command; otherwise, returns general help for the FTP server (usually a list of supported commands).

LIST
Syntax: LIST remote-filespec
If remote-filespec refers to a file, sends information about that file. If remote-filespec refers to a directory, sends information about each file in that directory. remote-filespec defaults to the current directory. This command must be preceded by a PORT or PASV command.

MDTM
Syntax: MDTM remote-filename
Returns the last-modified time of the given file on the remote host in the format "YYYYMMDDhhmmss": YYYY is the four-digit year, MM is the month from 01 to 12, DD is the day of the month from 01 to 31, hh is the hour from 00 to 23, mm is the minute from 00 to 59, and ss is the second from 00 to 59.

MKD
Syntax: MKD remote-directory
Creates the named directory on the remote host.

MODE
Syntax: MODE mode-character

Sets the transfer mode to one of:

  • S - Stream
  • B - Block
  • C - Compressed

The default mode is Stream.

NLST
Syntax: NLST remote-directory
Returns a list of filenames in the given directory (defaulting to the current directory), with no other information. Must be preceded by a PORT or PASV command.

NOOP
Syntax: NOOP
Does nothing except return a response.

PASS
Syntax: PASS password
After sending the USER command, send this command to complete the login process. (Note, however, that an ACCT command may have to be used on some systems.)

PASV
Syntax: PASV
Tells the server to enter "passive mode". In passive mode, the server will wait for the client to establish a connection with it rather than attempting to connect to a client-specified port. The server will respond with the address of the port it is listening on, with a message like:
227 Entering Passive Mode (a1,a2,a3,a4,p1,p2)
where a1.a2.a3.a4 is the IP address and p1*256+p2 is the port number.

PORT
Syntax: PORT a1,a2,a3,a4,p1,p2
Specifies the host and port to which the server should connect for the next file transfer. This is interpreted as IP address a1.a2.a3.a4, port p1*256+p2.

PWD
Syntax: PWD
Returns the name of the current directory on the remote host.

QUIT
Syntax: QUIT
Terminates the command connection.

REIN*
Syntax: REIN
Reinitializes the command connection - cancels the current user/password/account information. Should be followed by a USER command for another login.

REST
Syntax: REST position
Sets the point at which a file transfer should start; useful for resuming interrupted transfers. For nonstructured files, this is simply a decimal number. This command must immediately precede a data transfer command (RETR or STOR only); i.e. it must come after any PORT or PASV command.

RETR
Syntax: RETR remote-filename
Begins transmission of a file from the remote host. Must be preceded by either a PORT command or a PASV command to indicate where the server should send data.

RMD
Syntax: RMD remote-directory
Deletes the named directory on the remote host.

RNFR
Syntax: RNFR from-filename
Used when renaming a file. Use this command to specify the file to be renamed; follow it with an RNTO command to specify the new name for the file.

RNTO
Syntax: RNTO to-filename
Used when renaming a file. After sending an RNFR command to specify the file to rename, send this command to specify the new name for the file.

SITE*
Syntax: SITE site-specific-command
Executes a site-specific command.

SIZE
Syntax: SIZE remote-filename
Returns the size of the remote file as a decimal number.

STAT
Syntax: STAT remote-filespec
If invoked without parameters, returns general status information about the FTP server process. If a parameter is given, acts like the LIST command, except that data is sent over the control connection (no PORT or PASV command is required).

STOR
Syntax: STOR remote-filename
Begins transmission of a file to the remote site. Must be preceded by either a PORT command or a PASV command so the server knows where to accept data from.

STOU
Syntax: STOU
Begins transmission of a file to the remote site; the remote filename will be unique in the current directory. The response from the server will include the filename.

STRU
Syntax: STRU structure-character

Sets the file structure for transfer to one of:

  • F - File (no structure)
  • R - Record structure
  • P - Page structure

The default structure is File.

SYST
Syntax: SYST
Returns a word identifying the system, the word "Type:", and the default transfer type (as would be set by the TYPE command). For example: UNIX Type: L8

TYPE
Syntax: TYPE type-character second-type-character

Sets the type of file to be transferred. type-character can be any of:

  • A - ASCII text
  • E - EBCDIC text
  • I - image (binary data)
  • L - local format

For A and E, the second-type-character specifies how the text should be interpreted. It can be:

  • N - Non-print (not destined for printing). This is the default if second-type-character is omitted.
  • T - Telnet format control (<CR>, <FF>, etc.)
  • C - ASA Carriage Control

For L, the second-type-character specifies the number of bits per byte on the local system, and may not be omitted.

USER
Syntax: USER username
Send this command to begin the login process. username should be a valid username on the system, or "anonymous" to initiate an anonymous login.

"Transcribed fromt the various books I have lying around the room"

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