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telnet



Copyright Phillip Farrell. Last revision June 8, 2006

Telnet is the original Internet standard remote login program. It sends your password over the network in plain text format. Use the ssh family of programs for greater security.

On Unix systems, you start a remote login session to a remote computer by typing the command

telnet hostname

You substitute the IP hostname or address of the remote computer for hostname.

You will be prompted to enter a user account and password on the remote system. Once authenticated, your terminal window is now in continuous communication with the remote system, and you can enter commands and run programs on the remote system.

When you log out from the remote system, the telnet program will automatically exit on your local system.

Command line implementations of telnet have an "escape character", usually CTRL-] (hold down the "Control" key and press the "]" key), that temporarily suspends the connection to the remote machine and lets you give commands to the local telnet program. The most important use is to quit telnet (and thus close the connection) when your terminal gets frozen on the remote system. To do this, press the escape character and then give the command quit to the telnet> prompt that will be printed on the screen. For sessions orginating from Macintosh or Windows systems, you can simply close the terminal session window to abort a frozen connection.

Newer versions of telnet on Unix systems, Macintosh computers, and Windows PCs will automatically propagate your terminal type to the remote system, but for some older telnet implementations, you may need to set terminal type on the remote system, either in response to a prompt, or with the command set term=type (on Unix remote systems running the C-shell, like pangea). Try the actual type of your terminal first, for example, tvi925 or vt102. If vi or other programs that manipulate the screen do not seem to work, then try setting your terminal to type vt100 on the remote system. This is the most common terminal type standard.

telnet only provides a text terminal connection to the remote system. If you need full graphics capabilities, you should use the X Window system.

Note that telnet simply passes your login password over the network as clear text. In some circumstances, this can be captured by a "packet sniffing" program running on a machine on the same network as you or your remote client, and then used by an unauthorized person to login to your account. On the Stanford campus, the recommended telnet client programs for desktop computers (MacLeland/Samson and PCLeland/Samson) use the kerberos authentication method to provide completely encrypted telnet sessions to guard against this problem. Another common remote login program that accomplishes the same result is "ssh" (secure shell). Most campus servers support this as well as kerberos.

More information about secure logins to pangea can be found in the page describing pangea accounts.

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