The FTP protocol

FTP (File Transfer Protocol) - is part of the protocol stack TCP / IP, is used to copy files from one computer to another over a network. Exchange of data in the FTP organized on the principle of “client-server”. In this case, both computers must support the respective roles of FTP: one must be a client of FTP, and another - the server FTP. Figure 7.2.11 shows the model of the protocol.

In the FTP, connection is initiated by the protocol interpreterof the user. Flow control is carried out by the control channel in the standardprotocol TELNET. FTP commands are generated by user protocol interpreter and are transmitted to the server. Server responses are sent to the user also through the management channel. In general, the user is able to establish contact with the server protocol interpreter and different from the user interpreter means.

The FTP commands determine settings of the data transmission channel and the process of transmission. They also determine the nature of the work of local and remote file systems.

Session of management initiates the data channel. At the organization of the data transmission channel, sequence of actions is another, different from organization of the control channel. In this case, the server initiates adata exchange in accordance with the agreed in the session control of parameters.The data channel is set to the same computer as the control channel through which configuring the data channel is carried out. The data channel can be used for both reception and data transmission.

To access a remote computer the FTP protocol is used the following command - ftp host name, as the name of the nodethrough which the connection is carry out, can be used or IP-address or symbolic name of the computer. For example: ftp.microsoft.com or ftp 192.168.0.250.

Figure 7.2.11 – The diagram of FTP protocol work

The ftp command opens a session on a remote computer. After opening the session can be performed the work with directories and files pf the remote computer using the following commands:

- bye - Ends the session of FTP-connection to a remote computer with an exit from the program ftp;

- ls - Displays abbreviated list of files and subdirectories in a remote directory;

- Pwd - displays the name of the current directory on the remote computer;

- Send - copying a local file on a remote computer using the current settings such as uploaded files. Syntax - send local-file, where the local-file - Specifies the name of a local file for copying.

Дата добавления: 2014-12-27