ftpd

File Transfer Protocol is another standard Internet protocol for transmitting files between computers over TCP/IP connections. It is an application layer protocol. It was first created in 1971 to transfer data between a client and a server. To use this protocol, a computer’s FTP client application is required to send and receive data from a server running an FTP daemon (FTPd). The File Transfer Protocol (FTP) is client-server protocols that work on two channels between client and server:

·         Command channel for controlling the conversation between host and server

·         Data channel for transmitting and receiving files between client and server

Clients initiate a connection to the servers to manage traffic using port 21, consisting of client commands and server replies. After the client commands and the server replies, the client establishes the second connection to the server to transfer actual data using TCP port 20. The connection to port 20 is established every time there is data to be transferred. The figure below illustrates the File Transfer Protocol (FTP) connection.

Depending on user rights, the FTP client can download, upload, delete, rename, move, and copy data on a server. A user typically needs to log on to the FTP server, such as https://www.goanywhere.com/solutions/secure-ftp, while some servers use anonymous users for some or all of their content available without login.

The File Transfer Protocol sessions work in two modes: passive and active. In active mode, when a client opens a session via a command channel request, the server then opens a data connection back to the client and starts transferring data.

In passive mode, the server, as an alternative, uses the command channel to send the client the information required to open a data channel. Because the client has initiated all connections in the passive mode, it works better across firewalls and NAT. The FTP client can work via a simple command-line interface with a graphical user interface (GUI), and the Web browsers can also serve as FTP clients.