FTP File Transfer Protocol

File Transfer Protocol (Ftp:file Transfer Protocol) allows files to be shared between hosts. FTP uses TCP to generate a virtual connection to control information and then generate a separate TCP connection for data transfer. Control connections use similar TELNET protocols to Exchange commands and messages between hosts.

The main functions of FTP are as follows:

Provides sharing of files (computer programs/data), supports the indirect use of remote computers, and users are not affected by the differences between different types of host file memory systems; reliable and efficient transmission of data.

FTP, although it can be directly used by end users, but its application is mainly through the implementation of the program.

The FTP control frame refers to Telnet exchange information, including Telnet commands and options. However, most FTP control frames are simple ASCII text that can be divided into FTP commands or FTP messages. An FTP message is a response to an FTP command that consists of an answer code with interpreted text.

Protocol structure

Command	Describe
Abor	Interrupt Data Connection Program
ACCT <account>	System Privileged Account
ALLO <bytes>	Allocating bytes to file storage on the server
AppE <filename>	Add file to server file with same name
Cdup <dir path>	Change the parent directory on the server
CWD <dir path>	Change the working directory on the server
DELE <filename>	Delete the specified file on the server
Help <command>	Returns the specified command information
LIST <name>	If it is a filename, list file information and, if it is a directory, lists the files
MODE <mode>	Transfer mode (s= flow mode, b= block mode, c= compression mode)
MKD <directory>	Set up the specified directory on the server
NLST <directory>	Lists the contents of the specified directory
NOOP	No action, except recognition from the server
Pass <password>	System Login Password
PASV	Requesting a server to wait for a data connection
PORT <address>	IP address and two-byte port ID
Pwd	Show Current working directory
QUIT	To exit the login from the FTP server
REIN	Reinitialize Login Status Connection
REST <offset>	Restart file delivery by a specific offset
RETR <filename>	Retrieve (copy) a file from the server
RMD <directory>	Delete the specified directory on the server
RNFR <old path>	renaming old paths
Rnto <new path>	Renaming the new Path
SITE <params>	Site-specific parameters provided by the server
Smnt <pathname>	Mount the specified file structure
STAT <directory>	Returns information on the current program or directory
STOR <filename>	Save (copy) files to the server
Stou <filename>	Save file to server name
Stru <type>	Data structure (f= file, r= record, p= page)
Syst	Return to the operating system used by the server
TYPE <data type>	Data type (a=ascii,e=ebcdic,i=binary)
USER <username>>	User name for System login

The standard FTP information is as follows:

Response code	Explanatory notes
110	Restart mark on new file indicator
120	Server readiness Time (in minutes)
125	Open data connection, start transmission
150	Open connection
200	Success
202	Command not executed
211	System Status Reply
212	Directory Status reply
213	File status reply
214	Help message reply
215	System type Reply
220	Service Ready
221	Exit Network
225	Open Data Connection
226	End data Connection
227	Enter passive mode (IP address, ID Port)
230	Log on to the Internet
250	File Behavior complete
257	Path name creation
331	Password required
332	Request account Number
350	File Behavior paused
421	Service shutdown
425	Unable to open data connection
426	End Connection
450	File not available
451	Local error encountered
452	Low disk space
500	Invalid command
501	Error parameters
502	Command not executed
503	Error instruction sequence
504	Invalid command arguments
530	Network not logged in
532	Storage file requires account number
550	File not available
551	Type of page not known
552	Storage allocation exceeded
553	File name not allowed