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telnet(1)							    telnet(1)



NAME

  telnet - Provides the	TELNET interface for logging in	to a remote host

SYNOPSIS

  telnet [-d] [-l user]	[-n trace_file]	[host] [port]

  The telnet command implements	the TELNET protocol, which allows remote
  login	to other hosts.

OPTIONS

  -d  Turns debugging mode on.

  -l user
      Sends user to the	remote system as the value for the variable USER when
      connecting to the	remote system, if the remote system understands	the
      ENVIRON option. This option can also be used with	the open command.

  -n trace_file
      Records network trace information	in the file specified by trace_file.

DESCRIPTION

  The telnet command uses the Transmission Control Protocol/Internet Protocol
  (TCP/IP) to communicate with other hosts in the network. The telnet command
  operates in two different modes: command mode	and input mode.	 When issued
  without arguments, telnet enters command mode, as indicated by the telnet>>
  prompt.  Command mode	can also be entered by typing the telnet Escape	char-
  acter	(initially ^]).	When in	command	mode, the normal terminal editing
  conventions are available.

  In command mode, the subcommands listed in the SUBCOMMANDS section can be
  entered.  Some of these subcommands return you to the	remote session upon
  completion.  For those that do not, pressing <&lt;Return>&gt;	returns	you to the
  remote session.

  If telnet is issued with arguments, it performs an open subcommand with
  those	arguments, then	enters input mode. Once	a connection is	opened,	tel-
  net attempts to enable the TELNET LINEMODE option.  If this fails, telnet
  reverts to one of two	input modes: either character-at-a-time	or old line-
  by-line mode,	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 relays that information.	 The
  remote system	also relays 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 (in	most cases)
  only completed lines are sent	to the remote host. The	local echo character
  (initially ^E) can 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 BRK. There are options (see toggle autoflush and
  toggle autosynch below) that 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).

  The telnet command uses the default Type-of-Service value recommended	by
  RFC 1060, which is as	follows:

  telnet Low delay

  You can configure this value by specifying it	in the /etc/iptos file.	For
  more information, see	iptos(4).

SUBCOMMANDS

  For each of the subcommands in the following list, you only need to type
  enough letters to uniquely identify the command.  (For example, q is suffi-
  cient	for the	quit subcommand.) This is also true for	the arguments to the
  mode,	set, toggle, unset, slc, and display commands.

  The subcommands for telnet are as follows:

  ? [subcommand]
      Requests help on telnet.	Without	arguments, telnet prints a help	sum-
      mary.  If	a subcommand is	specified, telnet prints help information for
      just that	subcommand.

  close
      Closes the telnet	connection and returns to command mode.

  display [argument]
      Displays all of the set and toggle values	if no argument is specified;
      otherwise, lists only those values that match argument.

  environ argument ...
      Manipulates the variables	that can be sent through the telnet ENVIRON
      option.  The initial set of variables is taken from the user's environ-
      ment, with only the USER and DISPLAY variables being exported.

      Valid arguments for the environ subcommand are as	follows:

      define variable value
	  Defines variable to have the specified value.	 Any variables
	  defined by this command are automatically exported.  value can be
	  enclosed in single or	double quotes so that tabs and spaces can be
	  included.

      undefine variable
	  Removes variable from	the list of environment	variables.

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

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

      list
	  Lists	the current set	of environment variables.  Those marked	with
	  an * (asterisk) are sent automatically; other	variables are sent
	  only if explicitly requested.

  mode type
      The type option 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 is entered.

      ?	  Prints out help information for the mode command.

      character
	  Disables the LINEMODE	option,	or, if the remote side does not
	  understand the LINEMODE option, enters character-at-a-time mode.

      line
	  Enables the LINEMODE option, or, if the remote side does not under-
	  stand	the LINEMODE option, then attempts to enter old	line-by-line
	  mode.

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

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

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

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

  open host [port]
      Opens a connection to the	specified host.	 The host specification	can
      be a hostname, an	IPv4 address, an IPv6 address, or a source route.
      See the SOURCE ROUTING section for information on	source routing.	 If
      no port is given,	telnet attempts	to contact a TELNET server at the
      default port.

      When connecting to a nonstandard port, telnet omits any automatic	ini-
      tiation of TELNET	options.  When the port	number is preceded by a	-
      (dash), the initial option negotiation is	done. After establishing a
      connection, the .telnetrc	file in	the user's home	directory is opened.

      Lines beginning with a # (number sign) are comment lines.	 Blank lines
      are ignored.  Lines that begin without empty spaces are the start	of a
      machine entry.  The first	thing on the line is the name of the machine
      to which the user	is connected.  The rest	of the line and	successive
      lines that begin with empty spaces are assumed to	be telnet commands
      and are processed	as if they were	typed in manually to the telnet>&gt; com-
      mand prompt.

  quit
      Closes a TELNET connection and exits telnet.  An End-of-File in command
      mode also	closes the connection and exits.

  send argument	...
      Sends one	or more	arguments (special character sequences)	to the remote
      host.  (Not all hosts will respond to all	of these sequences.) Multiple
      arguments	are separated by spaces.  The following	arguments can be
      used:

      ?	  Prints help information for the send subcommand.

      abort
	  Sends	the TELNET ABORT (Abort	Processes) sequence.

      ao  Sends	the TELNET AO (Abort Output) sequence, which causes the
	  remote host to flush all output from the remote system to the	local
	  terminal.

      ayt Sends	the TELNET AYT (Are You	There) sequence, to which the remote
	  system can respond.

      brk Sends	the TELNET BRK (Break) sequence, which might have signifi-
	  cance	to the remote system.

      ec  Sends	the TELNET EC (Erase Character)	sequence, which	causes the
	  remote host to erase the last	character entered.

      el  Sends	the TELNET EL (Erase Line) sequence, which causes 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 (^]	by default).

      ga  Sends	the TELNET GA (Go Ahead) sequence, which provides the remote
	  system with a	mechanism to signal the	local system to	return con-
	  trol to the user.

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

      ip  Sends	the TELNET IP (Interrupt Process) sequence, which causes the
	  remote system	to terminate the currently running process.

      nop Sends	the TELNET NOP (No Operation) sequence.

      susp
	  Sends	the TELNET SUSP	(Suspend Process) sequence.

      synch
	  Sends	the TELNET SYNC	sequence, which	causes the remote system to
	  discard all previously typed input that has not yet been read.
	  This sequence	is sent	as TCP urgent data.

  set variable value
      Sets a telnet variable to	the specified value or to true.	 The off spe-
      cial value turns off the function	associated with	the variable name
      entered; this is equivalent to using the unset command.  The unset com-
      mand disables or sets to false any of the	specified functions.  The
      values of	variables can be queried with the display subcommand.  The
      variables	that can be set	or unset, but not toggled, are listed here.
      In addition, any of the variables	for the	toggle subcommand can be
      explicitly set or	unset by using the set and unset commands.

      ?	  Displays the legal set (unset) commands.

      echo
	  Toggles between enabling and suppressing local echo of entered
	  characters.  Local echo is used for normal processing, while
	  suppressing the echo is used for entering text that should not
	  appear on the	display, such as passwords.  This variable is ini-
	  tially ^E, and can only be used in line-by-line mode.

      eof Defines the End-of-File character for	telnet.	 When telnet is	in
	  line-by-line mode, entering the eof character	as the first charac-
	  ter on a line	sends the character to the remote host.	 The initial
	  value	for the	eof character is the local terminal's End-of-File
	  character.

      erase
	  Defines the erase character for telnet.  When	telnet is in
	  character-at-a-time mode and localchars is true, typing the erase
	  character sends the TELNET EC	sequence to the	remote host.  The
	  initial value	for the	erase character	is the local terminal's	erase
	  character.

      escape
	  Specifies the	telnet escape character	(initially ^]),	which puts
	  telnet into command mode when	connected to a remote host.

      flushoutput
	  Defines the flush character for telnet.  When	localchars is true,
	  typing the flushoutput character sends the TELNET AO sequence	to
	  the remote host. The initial value for the flush character is	the
	  terminal's flush character.

      forw1

      forw2
	  Defines alternate end-of-line	character.

      interrupt
	  Defines the interrupt	character for telnet.  When localchars is
	  true,	typing the interrupt character sends the TELNET	IP sequence
	  to the remote	host. The initial value	for the	interrupt character
	  is the local terminal's interrupt character.

      kill
	  Defines the kill character for telnet.  When telnet is in
	  character-at-a-time mode and localchars is true, typing the kill
	  character sends the TELNET EL	sequence to the	remote host.  The
	  initial value	for the	kill character is the local terminal's kill
	  character.

      lnext
	  Defines the lnext (literal next) character for telnet. If telnet is
	  operating in old line-by-line	mode and localchars is true, this
	  character is taken to	be the terminal's lnext	character. The ini-
	  tial value for the lnext character is	the local terminal's lnext
	  character.

      quit
	  Defines the quit character for telnet.  When localchars is true,
	  typing the quit character sends the TELNET BRK sequence to the
	  remote host.	The initial value for the quit character is the	local
	  terminal's quit character.

      reprint
	  Defines the terminal's reprint character, if telnet is operating in
	  LINEMODE or old line-by-line mode. The initial value for the
	  reprint character is the terminal's reprint character.

      start
	  Defines the terminal's start character, if the TELNET	TOGGLE-FLOW-
	  CONTROL option was enabled.  The initial value for the start char-
	  acter	is the terminal's start	character.

      stop
	  Defines the terminal's stop character, if the	TELNET TOGGLE-FLOW-
	  CONTROL option was enabled. The initial value	for the	stop charac-
	  ter is the terminal's	stop character.

      susp
	  Sends	a TELNET SUSP sequence (see send susp) to the remote host, if
	  telnet is in localchars mode,	or LINEMODE is enabled,	and the
	  suspend character is typed. The initial value	for the	suspend	char-
	  acter	is the terminal's suspend character.

      tracefile
	  Specifies the	file to	which the output, caused by netdata or option
	  tracing being	true, is written.  If it is set	to a - (dash), then
	  tracing information is written to standard output (the default).

      worderase
	  Defines the terminal's worderase character, if telnet	is operating
	  in LINEMODE or old line-by-line mode.	 The initial value for the
	  worderase character is taken to be the terminal's worderase charac-
	  ter.

  slc state
      Sets or changes the state	of the special characters when the TELNET
      LINEMODE option is enabled (Set Local Characters).  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.

      export
	  Switches 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
	  Switches 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.

      check
	  Verifies the current settings	for the	current	special	characters.
	  The remote side is requested to send all the current special char-
	  acter	settings, and if there are any discrepancies with the local
	  side,	the local side switches	to the remote value.

      ?	  Prints out help information for the slc command.

  status
      Shows the	current	status of telnet.  This	includes the host to which
      you are connected, as well as the	current	mode.

  toggle argument ...
      Toggles one or more arguments that control how telnet responds to
      events.  Possible	values are true	and false. These options can be
      explicitly set to	true or	false with the set and unset subcommands.
      Multiple arguments are separated by spaces.  The display subcommand can
      be used to query the current setting of each argument.

      The following arguments can be used:

      ?	  Displays valid arguments to toggle.

      autoflush
	  If autoflush and localchars are both true and	the AO,	interrupt,
	  and quit characters are recognized and transformed into TELNET
	  sequences, telnet does not display any data on the user's terminal
	  until	the remote system acknowledges (with a TELNET timing mark
	  option) that it has processed	those TELNET sequences.	The initial
	  value	of autoflush is	true if	the terminal has not done an stty
	  noflsh, and false if it has.

      autosynch
	  If autosynch and localchars are both true, then typing the inter-
	  rupt or quit character sends that character's	TELNET sequence, fol-
	  lowed	by the TELNET SYNC sequence.  This procedure causes the
	  remote host to discard all previously	typed input until both of the
	  telnet sequences are read and	acted upon.  The initial value of
	  this toggle is false.

      binary
	  Enables or disables the TELNET BINARY	option on both input and out-
	  put.

      inbinary
	  Enables or disables the TELNET BINARY	option on input.

      outbinary
	  Enables or disables the TELNET BINARY	option on output.

      crlf
	  Toggles carriage-return feature. When	true, carriage-returns are
	  sent as carriage-return/linefeed.  When false, carriage-returns are
	  sent as carriage-return/NULL.	 The initial value for this toggle is
	  false.

      crmod
	  Toggles carriage-return mode.	 When set to true, most	carriage-
	  return characters received from the remote host are mapped into a
	  carriage-return followed by a	linefeed.  This	mode does not affect
	  the characters typed by the user, only those received	from the
	  remote host.	This mode is useful when the remote host sends only a
	  carriage-return and not a linefeed.  The initial value of this tog-
	  gle is false.

      debug
	  Toggles debugging at the socket level.  This argument	can only be
	  entered by a user with superuser privileges.	The initial value of
	  this toggle is false.

      localchars
	  Determines the handling of telnet special characters.	 When this
	  value	is true, the erase, flush, interrupt, kill, and	quit charac-
	  ters are recognized locally and transformed into the appropriate
	  TELNET control sequences (EC,	AO, IP,	BRK, and EL, respectively).
	  When this value is false, these special characters are sent to the
	  remote host as literal characters. The initial value of localchars
	  is true in 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, quit	is sent	as abort, and eof and suspend are sent as eof
	  and susp (see	the send subcommand).

      netdata
	  Toggles the display of all network data (in hexadecimal format).
	  The data is written to standard output unless	a trace_file is
	  specified with the -n	option on the telnet command line. The
	  initial value	of this	toggle is false.

      options
	  Toggles the display of internal TELNET protocol processing options,
	  such as terminal negotiation and local or remote echo	of charac-
	  ters.	The initial value of this toggle is false, indicating that
	  the current options are not displayed.

      prettydump
	  When the netdata toggle is enabled and prettydump is also enabled,
	  the output from the netdata toggle appears in	a more readable	for-
	  mat.	Spaces are placed between the characters in the	output,	and
	  the beginning	of any TELNET escape sequence is preceded by an	*
	  (asterisk) to	aid in locating	it.

      termdata
	  Toggles printing of hexadecimal terminal data	(used for debugging).

  z   Suspends TELNET execution	and returns you	to your	original login shell.
      This subcommand works only when you are using csh	or ksh.

SOURCE ROUTING

  You can specify a source route to a destination system in either command
  mode or input	mode by	using the following syntax for host:

       [!]@hop@hop@hop...@host [-V {4|6}]

  Each hop can be an IPv4 address, IPv6	address, or host name.	If you use
  addresses, you must use the same address type	for each hop (either all IPv4
  addresses or all IPv6	addresses).

  There	are two	type of	source routes: strict and loose.  A strict source
  route	is one that does not do	any other lookups, and uses only the speci-
  fied hosts as	routes.	 The optional exclamation (!) character	preceding a
  source route indicates a strict source route.	 Strict	source routes are not
  supported in IPv6.

  Loose	source routes (those specified without ! character), try to use	the
  specified route as best as it	can.  However, in some instances an inter-
  mediate gateway may be used.

  The following	is an example of a strict source route.	 In this example,
  packets are sent to host1, which will	then forward them to host2.  Both
  host1	and host2 must have a direct link, otherwise the connection will be
  refused.

       !@host1@host2

  The following	is an example of a loose source	route.	In this	example,
  host1	and host2 do not have to have a	direct link, and may have a gateway
  or a router between them.

       @host1@host2

  If the user specifies	actual host names, telnet decides which	protocol to
  use as follows:









  ______________________________________________
  If any host has:    telnet uses this protocol:
  ______________________________________________
  IPv6 address only   IPv6
  IPv4 address only   IPv4
  ______________________________________________

  If all hosts have both IPv4 and IPv6 address,	telnet will use	IPv6.

  You can also modify which protocol is	used with the -V option. The -V
  option is only used in conjunction with a source route and must follow the
  source route.

  If you use the -V option and the option contradicts the outcome of the tel-
  net protocol selection, telnet prints	an error. If all hosts have both IPv4
  and IPv6 addresses, and you specify -V4, telnet will use IPv4.

NOTES

   1.  On some remote systems, echo has	to be turned off manually when in old
       line-by-line mode.

   2.  In old line-by-line mode	or LINEMODE, the terminal's End-of-File	char-
       acter is	only recognized	(and sent to the remote	system)	when it	is
       the first character on a	line.

EXAMPLES

   1.  To log in to host1 and do terminal type negotiation, enter:
	    telnet host1

       Information similar to the following is displayed on your screen:
	    Trying ...
	    Connected to host1
	    Escape character is	^]

	    login: _

   2.  To log in to remote host	host3 and then check the status	of the telnet
       program,	enter:
	    $ telnet host3

	    Trying ...
	    Connected to host3
	    Escape character is	^]

	    login: _

       Enter your login	ID and password	when you are prompted to do so.	Press
       ^] to receive the telnet>&gt; prompt. Enter the status subcommand at	the
       prompt.	Information similar to the following is	then displayed on
       your screen:
	    Connected to host3.
	    Operating in single	character mode.
	    Escape character is	'^]'.
	    _ Press <&lt;Return>&gt;
	    $_

       Upon completion of the status subcommand, you must press	<&lt;Return>&gt; to
       return to the remote prompt.







FILES

  ~/.telnetrc
      User-customized telnet startup values.


SEE ALSO

  Commands:  env(1), printenv(1), rexecd(8), rlogin(1),	rsh(1),	telnetd(8)

  Files:  iptos(4)