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.

FLAGS

  -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 flag 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 com-
  mand 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 character (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  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,

  telnet attempts to enable the TELNET LINEMODE option.	 If this fails, tel-
  net 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
  RFC1060, 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 either a hostname or an Internet address in dotted decimal form.  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> command 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
	  initially ^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 flag 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
	  characters.  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.

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> 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 
	    $_


       Upon completion of the status subcommand, you must press  to
       return to the remote prompt.

FILES

  ~/.telnetrc
	 User-customized telnet startup values.


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
       character is only recognized (and sent to the remote system) when it
       is the first character on a line.

RELATED INFORMATION

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

  Files: iptos(4)