Chapters 3 : Basic Internet Services

Sections 4 : Telnet : An Introduction


The telnet command is used to communicate with another host using the TELNET protocol. If telnet is invoked without the host argument, it enters command mode, indicated by its prompt (telnet>). In this mode, it accepts and executes the commands listed below. If it is invoked with arguments, it performs an open command with those arguments. This command allows a user to logon to a remote system and permits access to their account on the system.

How Telnet net functions:

telnet [host [port]]
Indicates the official name, an alias, or the Internet address of a remote host.

Indicates a port number (address of an application). If a number is not specified, the default telnet port is used.

Once a connection has been opened, telnet will attempt to enable the TELNET LINEMODE option. If this fails, then telnet will revert to one of two input modes: either ``character at a time'' or ``old line by line'' depending on what the remote system supports.

When LINEMODE is enabled, character processing is done on the local system, under the control of the remote system. When input editing or character echoing is to be disabled, the remote system will relay that information. The remote system will also relay changes to any special characters that happen on the remote system, so that they can take effect on the local system.

In ``character at a time'' mode, most text typed is immediately sent to the remote host for processing.

In ``old line by line'' mode, all text is echoed locally, and (normally) only completed lines are sent to the remote host. The ``local echo character'' (initially ``^E'') may be used to turn off and on the local echo (this would mostly be used to enter passwords without the password being echoed).


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