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

NAME
     telnet -- user interface to the TELNET protocol

SYNOPSIS
     telnet [-468EFKLNacdfruxy] [-S tos] [-X authtype] [-e escapechar] [-k realm] [-l user]
	    [-n tracefile] [-s src_addr] [host [port]]

DESCRIPTION
     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.

     Options:

     -4      Forces telnet to use IPv4 addresses only.

     -6      Forces telnet to use IPv6 addresses only.

     -8      Specifies an 8-bit data path.  This causes an attempt to negotiate the TELNET BINARY
	     option on both input and output.

     -E      Stops any character from being recognized as an escape character.

     -F      If Kerberos V5 authentication is being used, the -F option allows the local creden-
	     tials to be forwarded to the remote system, including any credentials that have
	     already been forwarded into the local environment.

     -K      Specifies no automatic login to the remote system.

     -L      Specifies an 8-bit data path on output.  This causes the BINARY option to be negoti-
	     ated on output.

     -N      Prevents IP address to name lookup when destination host is given as an IP address.

     -S tos  Sets the IP type-of-service (TOS) option for the telnet connection to the value tos,
	     which can be a numeric TOS value or, on systems that support it, a symbolic TOS name
	     found in the /etc/iptos file.

     -X atype
	     Disables the atype type of authentication.

     -a      Attempt automatic login.  This is now the default, so this option is ignored.  Cur-
	     rently, this sends the user name via the USER variable of the ENVIRON option if sup-
	     ported by the remote system.  The name used is that of the current user as returned
	     by getlogin(2) if it agrees with the current user ID, otherwise it is the name asso-
	     ciated with the user ID.

     -c      Disables the reading of the user's .telnetrc file.  (See the toggle skiprc command
	     on this man page.)

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

     -e escapechar
	     Sets the initial telnet escape character to escapechar.  If escapechar is omitted,
	     then there will be no escape character.

     -f      If Kerberos V5 authentication is being used, the -f option allows the local creden-
	     tials to be forwarded to the remote system.

     -k realm
	     If Kerberos authentication is being used, the -k option requests that telnet obtain
	     tickets for the remote host in realm realm instead of the remote host's realm, as
	     determined by krb_realmofhost(3).

     -l user
	     When connecting to the remote system, if the remote system understands the ENVIRON
	     option, then user will be sent to the remote system as the value for the variable
	     USER.  This option implies the -a option.	This option may also be used with the
	     open command.

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

     -r      Specifies a user interface similar to rlogin(1).  In this mode, the escape character
	     is set to the tilde (~) character, unless modified by the -e option.

     -s src_addr
	     Set the source IP address for the telnet connection to src_addr, which can be an IP
	     address or a host name.

     -u      Forces telnet to use AF_UNIX addresses only (e.g., UNIX domain sockets, accessed
	     with a file path).

     -x      Turns on encryption of the data stream if possible.  This is now the default, so
	     this option is ignored.

     -y      Suppresses encryption of the data stream.

     host    Indicates the official name, an alias, or the Internet address of a remote host.  If
	     host starts with a '/', telnet establishes a connection to the corresponding named
	     socket.

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

     When in rlogin mode, a line of the form ~.  disconnects from the remote host; ~ is the
     telnet escape character.  Similarly, the line ~^Z suspends the telnet session.  The line ~^]
     escapes to the normal telnet escape prompt.

     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 termi-
     nal (until the remote host acknowledges the TELNET sequence) and flush previous terminal
     input (in the case of quit and intr).

     While connected to a remote host, telnet command mode may be entered by typing the telnet
     ``escape character'' (initially ``^]'').  When in command mode, the normal terminal editing
     conventions are available.

     The following telnet commands are available.  Only enough of each command to uniquely iden-
     tify it need be typed (this is also true for arguments to the mode, set, toggle, unset, slc,
     environ, and display commands).

     auth argument ...
		The auth command manipulates the information sent through the TELNET AUTHENTICATE
		option.  Valid arguments for the auth command are:

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

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

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

     close	Close a TELNET session and return to command mode.

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

     encrypt argument ...
		The encrypt command manipulates the information sent through the TELNET ENCRYPT
		option.

		Valid arguments for the encrypt command are:

		disable type [input | output]
			      Disables the specified type of encryption.  If you omit the input
			      and output, both input and output are disabled.  To obtain a list
			      of available types, use the encrypt disable ? command.

		enable type [input | output]
			      Enables the specified type of encryption.  If you omit input and
			      output, both input and output are enabled.  To obtain a list of
			      available types, use the encrypt enable ? command.

		input	      This is the same as the encrypt start input command.

		-input	      This is the same as the encrypt stop input command.

		output	      This is the same as the encrypt start output command.

		-output       This is the same as the encrypt stop output command.

		start [input | output]
			      Attempts to start encryption.  If you omit input and output, both
			      input and output are enabled.  To obtain a list of available types,
			      use the encrypt enable ? command.

		status	      Lists the current status of encryption.

		stop [input | output]
			      Stops encryption.  If you omit input and output, encryption is on
			      both input and output.

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

     environ arguments ...
		The environ command is used to manipulate the variables that may be sent through
		the TELNET ENVIRON option.  The initial set of variables is taken from the users
		environment, with only the DISPLAY and PRINTER variables being exported by
		default.  The USER variable is also exported if the -a or -l options are 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 exported.  The value may be
			    enclosed in single or double quotes so that tabs and spaces may be
			    included.

		undefine variable
			    Remove variable from the list of environment variables.

		export variable
			    Mark the variable variable to be exported to the remote side.

		unexport variable
			    Mark the variable variable to not be exported unless explicitly asked
			    for by the remote side.

		list	    List the current set of environment variables.  Those marked with a *
			    will be sent automatically, other variables will only be sent if
			    explicitly requested.

		?	    Prints out help information for the environ command.

     logout	Sends the TELNET LOGOUT option to the remote side.  This command is similar to a
		close command; however, if the remote side does not support the LOGOUT option,
		nothing happens.  If, however, the remote side does support the LOGOUT option,
		this command should cause the remote side to close the TELNET connection.  If the
		remote side also supports the concept of suspending a user's session for later
		reattachment, the logout argument indicates that you should terminate the session
		immediately.

     mode type	Type is one of several options, depending on the state of the TELNET session.
		The remote host is asked for permission to go into the requested mode.	If the
		remote host is capable of entering that mode, the requested mode will be entered.

		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 server at the default port.  The host specification
		may be either a host name (see hosts(5)), an Internet address specified in the
		``dot notation'' (see inet(3)), or IPv6 host name or IPv6 coloned-hexadecimal
		addreess.  The -l option may be used to specify the user name to be passed to the
		remote system via the ENVIRON option.  When connecting to a non-standard port,
		telnet omits any automatic initiation of TELNET options.  When the port number is
		preceded by a minus sign, the initial option negotiation is done.  After estab-
		lishing a connection, the file .telnetrc in the users home directory is opened.
		Lines beginning with a # are comment lines.  Blank lines are ignored.  Lines that
		begin without white space are the start of a machine entry.  The first thing on
		the line is the name of the machine that is being connected to.  The rest of the
		line, and successive lines that begin with white space are assumed to be telnet
		commands and are processed as if they had been typed in manually to the telnet
		command prompt.

     quit	Close any open TELNET session and exit telnet.	An end of file (in command mode)
		will also close a session and exit.

     send arguments
		Sends one or more special character sequences to the remote host.  The following
		are the arguments which may be specified (more than one argument may be specified
		at a time):

		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 system
			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 (initially ``^'').

		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 functions.  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 using the set and
		unset commands.

		ayt	If TELNET is in localchars mode, or LINEMODE is enabled, and the status
			character is typed, a TELNET AYT sequence (see send ayt preceding) 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 escape character.  If set, the normal telnet escape
			character is ignored unless it is preceded by this character at the
			beginning of a line.  This character, at the beginning of a line followed
			by a "."  closes the connection; when followed by a ^Z it suspends the
			telnet command.  The initial state is to disable the rlogin escape char-
			acter.

		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 start 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 stop 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.

     opie sequence challenge
		The opie command computes a response to the OPIE challenge.

     slc state	The slc command (Set Local Characters) is used to set or change the state of 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 peer one is connected to,
		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 listed above.  More than one argument may be specified.	The state
		of these flags may be interrogated with the display command.  Valid arguments
		are:

		authdebug     Turns on debugging information for the authentication code.

		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.

		autologin     If the remote side supports the TELNET AUTHENTICATION option telnet
			      attempts to use it to perform automatic authentication.  If the
			      AUTHENTICATION option is not supported, the user's login name are
			      propagated through the TELNET ENVIRON option.  This command is the
			      same as specifying -a option on the open command.

		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.

		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 suspend 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 any telnet escape sequence is preceded by
			      a '*' to aid in locating them.

		skiprc	      When the skiprc toggle is TRUE, telnet skips the reading of the
			      .telnetrc file in the users home directory when connections are
			      opened.  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.

		?	      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 command is speci-
		fied, 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.

SEE ALSO
     rlogin(1), rsh(1), hosts(5), nologin(5), telnetd(8)

FILES
     ~/.telnetrc  user customized telnet startup values

HISTORY
     The telnet command appeared in 4.2BSD.

     IPv6 support was added by WIDE/KAME project.

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.

BSD					 January 27, 2000				      BSD
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