Illustrated TCP/IP by Matthew G. Naugle Wiley Computer Publishing, John Wiley & Sons, Inc. ISBN: 0471196568   Pub Date: 11/01/98

Chapter 220
TELNET

The TELNET connection simply allows a terminal service over the TCP/IP network as if the terminal were directly connected. Remember that computers and terminals were connected by a cable and the terminals were directly attached to the host computer. The TELNET service provides a terminal service for the network. It allows for any terminal to attach to any computer over the network. It can emulate many different types of terminals, depending on the manufacturer of the TELNET program. There are TELNET programs that emulate DEC VTxxx series of terminals, IBM 3270 and 5250 terminals, and more.

The advantage to the TELNET program is that a user may log on to any host on the TCP/IP internet (provided security options are allowed). Sessions are set up over the TCP/IP network.

The slide shows a typical TELNET connection on a TCP/IP network.

The TELNET protocol uses TCP as its transport. The user starts the TELNET protocol at his or her workstation, usually by typing TELNET <domain name or IP address>. The TELNET application may be started with or without an argument. The argument allows a simpler procedure to be invoked so that the TELNET process will automatically try to connect to the host signified by the argument statement. The TELNET application starts and attempts to establish a connection to the remote device (by accessing the services of the Domain Name Server or directly with the IP address; DNS will be discussed later). If an argument is not supplied, the TELNET application waits for the user to issue an OPEN command connection using the DNS or an IP address.

TELNET