FTP
File Transfer Protocol (FTP) is a standard Internet Protocol for transmitting files between computers on the Internet over TCP/IP connections. FTP is a client-server protocol where a client will ask for a file, and a local or remote server will provide it.
File Transfer Protocol (FTP) is a standard Internet Protocol for transmitting files between computers on the Internet over TCP/IP connections. FTP is a client-server protocol where a client will ask for a file, and a local or remote server will provide it.
- FTP stands for File transfer protocol.
- FTP is a standard internet protocol provided by TCP/IP used for transmitting the files from one host to another.
- It is mainly used for transferring the web page files from their creator to the computer that acts as a server for other computers on the internet.
- It is also used for downloading the files to computer from other servers
It provide a two types of connection in FTP
1. What is control connection?
For sending control information like user identification, password, commands to change the remote directory, commands to retrieve and store files, etc., FTP makes use of control connection. The control connection is initiated on port number 21.
For sending control information like user identification, password, commands to change the remote directory, commands to retrieve and store files, etc., FTP makes use of control connection. The control connection is initiated on port number 21.
2. Data Connection: The Data Connection uses very complex rules as data types may vary. The data connection is made between data transfer processes. The data connection opens when a command comes for transferring the files and closes when the file is transferred.
File Transfer Protocol Client (FTP Client) mean?
A File Transfer Protocol client (FTP client) is a software utility that establishes a connection between a host computer and a remote server, typically an FTP server. An FTP client provides the dual-direction transfer of data and files between two computers over a TCP network or an Internet connection. An FTP client works on a client/server architecture, where the host computer is the client and the remote FTP server is the central server.
Structure of FTP
- File Structure – In file-structure there is no internal structure and the file is considered to be a continuous sequence of data bytes.
- Record Structure – In record-structure the file is made up of sequential records.
- Page Structure – In page-structure the file is made up of independent indexed pages.
Transmission modes of FTP
• FTP can transfer a file by using one of the following three modes:
1.Stream mode
• It is the default mode.
• File is transmitted as continuous stream of bytes to TCP.
• TCP is responsible for chopping data into segments of appropriate size.
• If data is simply a stream of bytes (file structure), no end-of-file is needed. EOF in this case is the closing of the data connection by the sender.
• If data is divided into records (record structure), each record has a I-byte EOR (End-of-Record) character and the end of the file has a I-byte EOF (End-of-file) character.
2.Block mode
• Data is delivered from FTP to TCP in blocks.
• Each block is preceded by 3 bytes header.
• The first byte is called the block descriptor.
• The second and third byte defines the size of the block in bytes.
3.Compressed mode
• Data is usually compressed if the file to be transmitted is very big.
• The compression method normally used in Run-length encoding.
• In a text file, usually spaces (blanks) are removed.
• In a binary file, null characters are compressed.
FTP COMMANDS
1.Transfer file command
GET- Get the file from remote computer.
PUT- Send one file.
SEND- Send single file.
2. Connect to remote host
USER- This command send the user identification to the server.
OPEN- Open address.
PASS- This command send the user password to the server.
3. Terminate session command.
CLOSE- Disconnect FTP but does not terminate user.
QUITE- This command is used for disconnect from the remote host and terminate FTP.
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