TELNET(1) — Series 300 and 800 Only

NAME

telnet − user interface to the TELNET protocol

SYNOPSIS

telnet [ host[ port] ]

DESCRIPTION

Telnet is used to communicate with another host using the TELNET protocol. If telnet is invoked without arguments, it enters command mode, indicated by its prompt (“telnet>”). In this mode, it accepts and executes the commands listed below. If telnet is invoked with arguments, it performs an open command (see below) with those arguments.

Once a connection has been opened, telnet enters input mode. In this mode, text typed is sent to the remote host. To issue telnet commands when in input mode, precede them with the telnet escape character (see the escape command below). When in command mode, the normal terminal editing conventions are available.

Telnet supports eight-bit characters when communicating with the server on the remote host. To use eight-bit characters you may need to reconfigure your terminal or the remote host appropriately; see stty(1). Note that some remote hosts may not provide the necessary support for eight-bit characters.

If at any time telnet is unable to read from or write to the connection to the server, the message “Connection closed by foreign host.” is printed on stderr, and telnet exits with a value of one.

Commands

The following commands are available in command mode. Only enough of each command to uniquely identify it need be typed.

open host [ port ]
Open a connection to the named host at the indicated port. If no port is specified, telnet attempts to contact a TELNET server at the standard TELNET port. The hostname can be either the official name or an alias as listed in /etc/hosts, or an Internet address specified in the dot notation used in the file /etc/hosts (see hosts(4)). If no hostname is given, telnet prompts for one.

close Close a TELNET session. If the session was started from command mode, then telnet returns to command mode; otherwise telnet exits.

quit Close any open TELNET session and exit telnet.

escape [ escape-char ]
Set the telnet escape character. Control characters may be specified as ^ followed by a single letter; for example, control-X is ^X. The default escape character is ^]. Some characters may conflict with your terminal configuration; such as, ^S, ^Q, and backspace. Using one of these characters as the escape character may not be possible or may cause problems communicating with the remote host; see stty(1) and tty(4).

status Show the current status of telnet. This includes the peer to which telnet is connected, along with the current escape character. Control characters are printed as above.

options Toggle viewing of TELNET options processing. When options viewing is enabled, all TELNET option negotiations are displayed. Options sent by telnet are displayed as “SENT”, while options received from the TELNET server are displayed as “RCVD”.

crmod Toggle carriage return mode. When this mode is enabled, any carriage return characters received from the remote host are mapped into a carriage return and a line feed. This mode does not affect those characters typed by the user, only those received. This mode is only required for some hosts that require the client to do local echoing.

? [ command ]
Get help. With no arguments, telnet prints a help summary. If a command is specified, telnet prints the help information available about that command only. Help information is limited to a one-line description of the command.

! [ shellcommand ]
Shell escape. The SHELL environment variable is checked for the name of a shell to use to execute the command. If no command is specified, then a shell is started and connected to the user’s terminal. If SHELL is undefined, then /bin/sh is used.

z Suspend the TELNET session. This command is only available on systems using csh. The z command will suspend the TELNET session and return the user to the shell that invoked telnet. The job may then be resumed with the “fg” command. (See csh(1)).

RETURN VALUE

In the event of an error, or if the TELNET connection is closed by the remote host, telnet returns a value of one. Otherwise it returns a zero.

DIAGNOSTICS

The following diagnostic messages are displayed by telnet:

telnet/tcp: Unknown service
Telnet was unable to find the telnet service entry in the /etc/services database file.

<hostname>: Unknown host
Telnet was unable to find an entry for the host name in /etc/hosts and was unable to convert the host name into an Internet address. Check to be sure you have entered the host name correctly and in the format listed in /etc/hosts.

Next step: Contact the system administrator to have an entry for the remote host added to the file.

< system call >: ...
An error occurred in the specified system call. See the appropriate manual page for a description of the error.

DEPENDENCIES

Implemented on the Series 300 and 800 only.

AUTHOR

UCB (University of California at Berkeley)

Museum

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