The Telecommunication Network Protocol (Telnet) is derived from ARPANET released in 1969. It is the earliest Internet application.
A Telnet connection is a Transmission Control Protocol (TCP) connection used to transmit data with interspersed Telnet control information. Telnet uses the client/server model to present an interactive interface that enables a terminal to remotely log in to a server. A user can log in to one host and then use Telnet to remotely log in to and configure and manage multiple hosts without having to connect each one to a terminal. Figure 1 shows the Telnet client/server model.
In Figure 1:
Telnet uses TCP for transmission.
All Telnet echo information is displayed on the terminal.
The server directly interacts with the pseudo terminal.
The server and client transmit commands and data over the TCP connection.
The client logs in to the server.
Use the STelnet protocol because this protocol is not secure.