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TELNET(1)			   BSD General Commands Manual				TELNET(1)

NAME
     telnet -- user interface to the TELNET protocol

SYNOPSIS
     telnet [-468ELadr] [-S tos] [-b address] [-e escapechar] [-l user] [-n tracefile] [host
	    [port]]

DESCRIPTION
     The telnet command is used for interactive communication with another host using the TELNET
     protocol. It begins in command mode, where it prints a telnet prompt ("telnet> "). If telnet
     is invoked with a host argument, it performs an open command implicitly; see the description
     below.

     Options:

     -4      Force IPv4 address resolution.

     -6      Force IPv6 address resolution.

     -8      Request 8-bit operation. This causes an attempt to negotiate the TELNET BINARY
	     option for both input and output. By default telnet is not 8-bit clean.

     -E      Disables the escape character functionality; that is, sets the escape character to
	     ``no character''.

     -L      Specifies an 8-bit data path on output.  This causes the TELNET BINARY option to be
	     negotiated on just output.

     -a      Attempt automatic login.  Currently, this sends the user name via the USER variable
	     of the ENVIRON option if supported by the remote system. The username is retrieved
	     via getlogin(3).

     -b address
	     Use bind(2) on the local socket to bind it to a specific local address.

     -d      Sets the initial value of the debug toggle to TRUE.

     -r      Emulate rlogin(1).  In this mode, the default escape character is a tilde. Also, the
	     interpretation of the escape character is changed: an escape character followed by a
	     dot causes telnet to disconnect from the remote host. A ^Z instead of a dot suspends
	     telnet, and a ^] (the default telnet escape character) generates a normal telnet
	     prompt. These codes are accepted only at the beginning of a line.

     -S tos  Sets the IP type-of-service (TOS) option for the telnet connection to the value tos.

     -e escapechar
	     Sets the escape character to escapechar. If no character is supplied, no escape
	     character will be used.  Entering the escape character while connected causes telnet
	     to drop to command mode.

     -l user
	     Specify user as the user to log in as on the remote system. This is accomplished by
	     sending the specified name as the USER environment variable, so it requires that the
	     remote system support the TELNET ENVIRON option. This option implies the -a option,
	     and may also be used with the open command.

     -n tracefile
	     Opens tracefile for recording trace information.  See the set tracefile command
	     below.

     host    Specifies a host to contact over the network.

     port    Specifies a port number or service name to contact. If not specified, the telnet
	     port (23) is used.

     Protocol:

     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 con-
     trol 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).

     If the LINEMODE option is enabled, or if the localchars toggle is TRUE (the default for
     ``old line by line``; see below), the user's quit, intr, and flush characters are trapped
     locally, and sent as TELNET protocol sequences to the remote side.  If LINEMODE has ever
     been enabled, then the user's susp and eof are also sent as TELNET protocol sequences, and
     quit is sent as a TELNET ABORT instead of BREAK There are options (see toggle autoflush and
     toggle autosynch below) which cause this action to flush subsequent output to the terminal
     (until the remote host acknowledges the TELNET sequence) and flush previous terminal input
     (in the case of quit and intr).

     Commands:

     The following telnet commands are available. Unique prefixes are understood as abbrevia-
     tions.

     auth argument ...
		The auth command controls the TELNET AUTHENTICATE protocol option.  If telnet was
		compiled without authentication, the auth command will not be supported.  Valid
		arguments are as follows:

		disable type  Disable the specified type of authentication.  To obtain a list of
			      available types, use the auth disable ? command.

		enable type   Enable the specified type of authentication.  To obtain a list of
			      available types, use the auth enable ? command.

		status	      List the current status of the various types of authentication.

		Note that the current version of telnet does not support authentication.

     close	Close the connection to the remote host, if any, and return to command mode.

     display argument ...
		Display all, or some, of the set and toggle values (see below).

     encrypt argument ...
		The encrypt command controls the TELNET ENCRYPT protocol option. If telnet was
		compiled without encryption, the encrypt command will not be supported.

		Valid arguments are as follows:

		disable type [input|output]
			      Disable the specified type of encryption.  If you do not specify
			      input or output, encryption of both is disabled.	To obtain a list
			      of available types, use ``encrypt disable ?''.

		enable type [input|output]
			      Enable the specified type of encryption.	If you do not specify
			      input or output, encryption of both is enabled.  To obtain a list
			      of available types, use ``encrypt enable ?''.

		input	      This is the same as ``encrypt start input''.

		-input	      This is the same as ``encrypt stop input''.

		output	      This is the same as ``encrypt start output''.

		-output       This is the same as ``encrypt stop output''.

		start [input|output]
			      Attempt to begin encrypting.  If you do not specify input or out-
			      put, encryption of both input and output is started.

		status	      Display the current status of the encryption module.

		stop [input|output]
			      Stop encrypting.	If you do not specify input or output, encryption
			      of both is stopped.

		type type     Sets the default type of encryption to be used with later ``encrypt
			      start'' or ``encrypt stop'' commands.

		Note that the current version of telnet does not support encryption.

     environ arguments...
		The environ command is used to propagate environment variables across the telnet
		link using the TELNET ENVIRON protocol option.	All variables exported from the
		shell are defined, but only the DISPLAY and PRINTER variables are marked to be
		sent by default.  The USER variable is marked to be sent if the -a or -l command-
		line options were used.

		Valid arguments for the environ command are:

		define variable value
			    Define the variable variable to have a value of value. Any variables
			    defined by this command are automatically marked for propagation
			    (``exported'').  The value may be enclosed in single or double quotes
			    so that tabs and spaces may be included.

		undefine variable
			    Remove any existing definition of variable.

		export variable
			    Mark the specified variable for propagation to the remote host.

		unexport variable
			    Do not mark the specified variable for propagation to the remote
			    host. The remote host may still ask explicitly for variables that are
			    not exported.

		list	    List the current set of environment variables.  Those marked with a *
			    will be propagated to the remote host. The remote host may still ask
			    explicitly for the rest.

		?	    Prints out help information for the environ command.

     logout	Send the TELNET LOGOUT protocol option to the remote host.  This command is simi-
		lar to a close command. If the remote host does not support the LOGOUT option,
		nothing happens.  But if it does, this command should cause it to close the con-
		nection.  If the remote side also supports the concept of suspending a user's
		session for later reattachment, the logout command indicates that the session
		should be terminated immediately.

     mode type	Type is one of several options, depending on the state of the session.	Telnet
		asks the remote host to go into the requested mode. If the remote host says it
		can, that mode takes effect.

		character     Disable the TELNET LINEMODE option, or, if the remote side does not
			      understand the LINEMODE option, then enter ``character at a time``
			      mode.

		line	      Enable the TELNET LINEMODE option, or, if the remote side does not
			      understand the LINEMODE option, then attempt to enter ``old-line-
			      by-line`` mode.

		isig (-isig)  Attempt to enable (disable) the TRAPSIG mode of the LINEMODE
			      option.  This requires that the LINEMODE option be enabled.

		edit (-edit)  Attempt to enable (disable) the EDIT mode of the LINEMODE option.
			      This requires that the LINEMODE option be enabled.

		softtabs (-softtabs)
			      Attempt to enable (disable) the SOFT_TAB mode of the LINEMODE
			      option.  This requires that the LINEMODE option be enabled.

		litecho (-litecho)
			      Attempt to enable (disable) the LIT_ECHO mode of the LINEMODE
			      option.  This requires that the LINEMODE option be enabled.

		?	      Prints out help information for the mode command.

     open host [[-l] user][- port]
		Open a connection to the named host.  If no port number is specified, telnet will
		attempt to contact a telnet daemon at the standard port (23).  The host specifi-
		cation may be a host name or IP address.  The -l option may be used to specify a
		user name to be passed to the remote system, like the -l command-line option.

		When connecting to ports other than the telnet port, telnet does not attempt
		telnet protocol negotiations. This makes it possible to connect to services that
		do not support the telnet protocol without making a mess. Protocol negotiation
		can be forced by placing a dash before the port number.

		After establishing a connection, any commands associated with the remote host in
		/etc/telnetrc and the user's .telnetrc file are executed, in that order.

		The format of the telnetrc files is as follows: Lines beginning with a #, and
		blank lines, are ignored.  The rest of the file should consist of hostnames and
		sequences of telnet commands to use with that host. Commands should be one per
		line, indented by whitespace; lines beginning without whitespace are interpreted
		as hostnames.  Lines beginning with the special hostname 'DEFAULT' will apply to
		all hosts.  Hostnames including 'DEFAULT' may be followed immediately by a colon
		and a port number or string.  If a port is specified it must match exactly with
		what is specified on the command line.	If no port was specified on the command
		line, then the value 'telnet' is used.	Upon connecting to a particular host, the
		commands associated with that host are executed.

     quit	Close any open session and exit telnet.  An end of file condition on input, when
		in command mode, will trigger this operation as well.

     send arguments
		Send one or more special telnet protocol character sequences to the remote host.
		The following are the codes which may be specified (more than one may be used in
		one command):

		abort	Sends the TELNET ABORT (Abort Processes) sequence.

		ao	Sends the TELNET AO (Abort Output) sequence, which should cause the
			remote system to flush all output from the remote system to the user's
			terminal.

		ayt	Sends the TELNET AYT (Are You There?) sequence, to which the remote sys-
			tem may or may not choose to respond.

		brk	Sends the TELNET BRK (Break) sequence, which may have significance to the
			remote system.

		ec	Sends the TELNET EC (Erase Character) sequence, which should cause the
			remote system to erase the last character entered.

		el	Sends the TELNET EL (Erase Line) sequence, which should cause the remote
			system to erase the line currently being entered.

		eof	Sends the TELNET EOF (End Of File) sequence.

		eor	Sends the TELNET EOR (End of Record) sequence.

		escape	Sends the current telnet escape character.

		ga	Sends the TELNET GA (Go Ahead) sequence, which likely has no significance
			to the remote system.

		getstatus
			If the remote side supports the TELNET STATUS command, getstatus will
			send the subnegotiation to request that the server send its current
			option status.

		ip	Sends the TELNET IP (Interrupt Process) sequence, which should cause the
			remote system to abort the currently running process.

		nop	Sends the TELNET NOP (No Operation) sequence.

		susp	Sends the TELNET SUSP (Suspend Process) sequence.

		synch	Sends the TELNET SYNCH sequence.  This sequence causes the remote system
			to discard all previously typed (but not yet read) input.  This sequence
			is sent as TCP urgent data (and may not work if the remote system is a
			4.2BSD system -- if it doesn't work, a lower case ``r'' may be echoed on
			the terminal).

		do cmd

		dont cmd

		will cmd

		wont cmd
			Sends the TELNET DO cmd sequence.  cmd can be either a decimal number
			between 0 and 255, or a symbolic name for a specific TELNET command.  cmd
			can also be either help or ? to print out help information, including a
			list of known symbolic names.

		?	Prints out help information for the send command.

     set argument value

     unset argument value
		The set command will set any one of a number of telnet variables to a specific
		value or to TRUE.  The special value off turns off the function associated with
		the variable. This is equivalent to using the unset command.  The unset command
		will disable or set to FALSE any of the specified variables.  The values of vari-
		ables may be interrogated with the display command.  The variables which may be
		set or unset, but not toggled, are listed here.  In addition, any of the vari-
		ables for the toggle command may be explicitly set or unset.

		ayt	If telnet is in localchars mode, or LINEMODE is enabled, and the status
			character is typed, a TELNET AYT sequence is sent to the remote host.
			The initial value for the "Are You There" character is the terminal's
			status character.

		echo	This is the value (initially ``^E'') which, when in ``line by line''
			mode, toggles between doing local echoing of entered characters (for nor-
			mal processing), and suppressing echoing of entered characters (for
			entering, say, a password).

		eof	If telnet is operating in LINEMODE or ``old line by line'' mode, entering
			this character as the first character on a line will cause this character
			to be sent to the remote system.  The initial value of the eof character
			is taken to be the terminal's eof character.

		erase	If telnet is in localchars mode (see toggle localchars below), and if
			telnet is operating in ``character at a time'' mode, then when this char-
			acter is typed, a TELNET EC sequence (see send ec above) is sent to the
			remote system.	The initial value for the erase character is taken to be
			the terminal's erase character.

		escape	This is the telnet escape character (initially ``^['') which causes entry
			into telnet command mode (when connected to a remote system).

		flushoutput
			If telnet is in localchars mode (see toggle localchars below) and the
			flushoutput character is typed, a TELNET AO sequence (see send ao above)
			is sent to the remote host.  The initial value for the flush character is
			taken to be the terminal's flush character.

		forw1

		forw2	If TELNET is operating in LINEMODE, these are the characters that, when
			typed, cause partial lines to be forwarded to the remote system.  The
			initial value for the forwarding characters are taken from the terminal's
			eol and eol2 characters.

		interrupt
			If telnet is in localchars mode (see toggle localchars below) and the
			interrupt character is typed, a TELNET IP sequence (see send ip above) is
			sent to the remote host.  The initial value for the interrupt character
			is taken to be the terminal's intr character.

		kill	If telnet is in localchars mode (see toggle localchars below), and if
			telnet is operating in ``character at a time'' mode, then when this char-
			acter is typed, a TELNET EL sequence (see send el above) is sent to the
			remote system.	The initial value for the kill character is taken to be
			the terminal's kill character.

		lnext	If telnet is operating in LINEMODE or ``old line by line`` mode, then
			this character is taken to be the terminal's lnext character.  The ini-
			tial value for the lnext character is taken to be the terminal's lnext
			character.

		quit	If telnet is in localchars mode (see toggle localchars below) and the
			quit character is typed, a TELNET BRK sequence (see send brk above) is
			sent to the remote host.  The initial value for the quit character is
			taken to be the terminal's quit character.

		reprint
			If telnet is operating in LINEMODE or ``old line by line`` mode, then
			this character is taken to be the terminal's reprint character.  The ini-
			tial value for the reprint character is taken to be the terminal's
			reprint character.

		rlogin	This is the rlogin mode escape character. Setting it enables rlogin mode,
			as with the r command-line option (q.v.)

		start	If the TELNET TOGGLE-FLOW-CONTROL option has been enabled, then this
			character is taken to be the terminal's start character.  The initial
			value for the kill character is taken to be the terminal's start charac-
			ter.

		stop	If the TELNET TOGGLE-FLOW-CONTROL option has been enabled, then this
			character is taken to be the terminal's stop character.  The initial
			value for the kill character is taken to be the terminal's stop charac-
			ter.

		susp	If telnet is in localchars mode, or LINEMODE is enabled, and the suspend
			character is typed, a TELNET SUSP sequence (see send susp above) is sent
			to the remote host.  The initial value for the suspend character is taken
			to be the terminal's suspend character.

		tracefile
			This is the file to which the output, caused by netdata or option tracing
			being TRUE, will be written.  If it is set to ``-'', then tracing infor-
			mation will be written to standard output (the default).

		worderase
			If telnet is operating in LINEMODE or ``old line by line`` mode, then
			this character is taken to be the terminal's worderase character.  The
			initial value for the worderase character is taken to be the terminal's
			worderase character.

		?	Displays the legal set (unset) commands.

     slc state	The slc command (Set Local Characters) is used to set or change the state of the
		the special characters when the TELNET LINEMODE option has been enabled.  Special
		characters are characters that get mapped to TELNET commands sequences (like ip
		or quit) or line editing characters (like erase and kill).  By default, the local
		special characters are exported.

		check	    Verify the current settings for the current special characters.  The
			    remote side is requested to send all the current special character
			    settings, and if there are any discrepancies with the local side, the
			    local side will switch to the remote value.

		export	    Switch to the local defaults for the special characters.  The local
			    default characters are those of the local terminal at the time when
			    telnet was started.

		import	    Switch to the remote defaults for the special characters.  The remote
			    default characters are those of the remote system at the time when
			    the TELNET connection was established.

		?	    Prints out help information for the slc command.

     status	Show the current status of telnet.  This includes the name of the remote host, if
		any, as well as the current mode.

     toggle arguments ...
		Toggle (between TRUE and FALSE) various flags that control how telnet responds to
		events.  These flags may be set explicitly to TRUE or FALSE using the set and
		unset commands.  More than one flag may be toggled at once.  The state of these
		flags may be examined with the display command.  Valid flags are:

		authdebug     Turns on debugging for the authentication code. This flag only
			      exists if authentication support is enabled.

		autoflush     If autoflush and localchars are both TRUE, then when the ao, or
			      quit characters are recognized (and transformed into TELNET
			      sequences; see set above for details), telnet refuses to display
			      any data on the user's terminal until the remote system acknowl-
			      edges (via a TELNET TIMING MARK option) that it has processed those
			      TELNET sequences.  The initial value for this toggle is TRUE if the
			      terminal user had not done an "stty noflsh", otherwise FALSE (see
			      stty(1)).

		autodecrypt   When the TELNET ENCRYPT option is negotiated, by default the actual
			      encryption (decryption) of the data stream does not start automati-
			      cally.  The autoencrypt (autodecrypt) command states that encryp-
			      tion of the output (input) stream should be enabled as soon as pos-
			      sible.

			      Note that this flag exists only if encryption support is enabled.

		autologin     If the remote side supports the TELNET AUTHENTICATION option,
			      telnet attempts to use it to perform automatic authentication.  If
			      the TELNET AUTHENTICATION option is not supported, the user's login
			      name is propagated using the TELNET ENVIRON option.  Setting this
			      flag is the same as specifying the a option to the open command or
			      on the command line.

		autosynch     If autosynch and localchars are both TRUE, then when either the
			      intr or quit characters is typed (see set above for descriptions of
			      the intr and quit characters), the resulting telnet sequence sent
			      is followed by the TELNET SYNCH sequence.  This procedure should
			      cause the remote system to begin throwing away all previously typed
			      input until both of the telnet sequences have been read and acted
			      upon.  The initial value of this toggle is FALSE.

		binary	      Enable or disable the TELNET BINARY option on both input and out-
			      put.

		inbinary      Enable or disable the TELNET BINARY option on input.

		outbinary     Enable or disable the TELNET BINARY option on output.

		crlf	      If this is TRUE, then carriage returns will be sent as <CR><LF>.
			      If this is FALSE, then carriage returns will be send as <CR><NUL>.
			      The initial value for this toggle is FALSE.

		crmod	      Toggle carriage return mode.  When this mode is enabled, most car-
			      riage return characters received from the remote host will be
			      mapped into a carriage return followed by a line feed.  This mode
			      does not affect those characters typed by the user, only those
			      received from the remote host.  This mode is not very useful unless
			      the remote host only sends carriage return, but never line feed.
			      The initial value for this toggle is FALSE.

		debug	      Toggles socket level debugging (useful only to the super user).
			      The initial value for this toggle is FALSE.

		encdebug      Turns on debugging information for the encryption code.  Note that
			      this flag only exists if encryption support is available.

		localchars    If this is TRUE, then the flush, interrupt, quit, erase, and kill
			      characters (see set above) are recognized locally, and transformed
			      into (hopefully) appropriate TELNET control sequences (respectively
			      ao, ip, brk, ec, and el; see send above).  The initial value for
			      this toggle is TRUE in ``old line by line'' mode, and FALSE in
			      ``character at a time'' mode.  When the LINEMODE option is enabled,
			      the value of localchars is ignored, and assumed to always be TRUE.
			      If LINEMODE has ever been enabled, then quit is sent as abort, and
			      eof and are sent as eof and susp, see send above).

		netdata       Toggles the display of all network data (in hexadecimal format).
			      The initial value for this toggle is FALSE.

		options       Toggles the display of some internal telnet protocol processing
			      (having to do with telnet options).  The initial value for this
			      toggle is FALSE.

		prettydump    When the netdata toggle is enabled, if prettydump is enabled the
			      output from the netdata command will be formatted in a more user-
			      readable format.	Spaces are put between each character in the out-
			      put, and the beginning of telnet escape sequences are preceded by a
			      '*' to aid in locating them.

		skiprc	      When the skiprc toggle is TRUE, telnet does not read the telnetrc
			      files.  The initial value for this toggle is FALSE.

		termdata      Toggles the display of all terminal data (in hexadecimal format).
			      The initial value for this toggle is FALSE.

		verbose_encrypt
			      When the verbose_encrypt toggle is TRUE, TELNET prints out a mes-
			      sage each time encryption is enabled or disabled.  The initial
			      value for this toggle is FALSE. This flag only exists if encryption
			      support is available.

		?	      Displays the legal toggle commands.

     z		Suspend telnet.  This command only works when the user is using the csh(1).

     ! [command]
		Execute a single command in a subshell on the local system.  If command is omit-
		ted, then an interactive subshell is invoked.

     ? [command]
		Get help.  With no arguments, telnet prints a help summary.  If a command is
		specified, telnet will print the help information for just that command.

ENVIRONMENT
     Telnet uses at least the HOME, SHELL, DISPLAY, and TERM environment variables.  Other envi-
     ronment variables may be propagated to the other side via the TELNET ENVIRON option.

FILES
     /etc/telnetrc  global telnet startup values
     ~/.telnetrc    user customized telnet startup values

HISTORY
     The Telnet command appeared in 4.2BSD.

NOTES
     On some remote systems, echo has to be turned off manually when in ``old line by line''
     mode.

     In ``old line by line'' mode or LINEMODE the terminal's eof character is only recognized
     (and sent to the remote system) when it is the first character on a line.

BUGS
     The source code is not comprehensible.

Linux NetKit (0.17)			 August 15, 1999		      Linux NetKit (0.17)
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