| TELNET(1) | General Commands Manual | TELNET(1) | 
telnet —
| telnet | [ -468acdEFfKLNrx] [-eescapechar] [-krealm] [-luser] [-ntracefile] [-Ppolicy] [-Stos] [-Xauthtype] [host
      [port]] | 
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:
-4telnet to use IPv4 addresses only.-6telnet to use IPv6 addresses only.-8TELNET BINARY option on both input and
    output.-E-F-F option allows the local credentials to be
      forwarded to the remote system, including any credentials that have
      already been forwarded into the local environment.-K-L-N-S
    tos-X
    atype-aUSER variable of the
      ENVIRON option if supported 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 associated with the
      user ID.-ctoggle skiprc command on this man
    page.)-ddebug toggle to
      TRUE.-e
    escape chartelnet escape character to
      escape char. If escape char is
      omitted, then there will be no escape character.-f-f option allows the local credentials to be
      forwarded to the remote system.-k
    realm-k
      option requests that telnet obtain tickets for the remote host in realm
      realm instead of the remote host's realm.-l
    userENVIRON 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
    tracefileset tracefile command below.-P
    policy-r-e option.-xtelnet 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 control 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).
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 identify it need be typed
    (this is also true for arguments to the mode,
    set, toggle,
    unset, slc,
    environ, and display
    commands).
auth
    argument ...TELNET AUTHENTICATE option. Valid arguments for
      the auth command are as follows:
    disable
        typeauth disable ?
          command.enable
        typeauth enable ?
          command.statusclosedisplay
    argument ...set and
      toggle values (see below).encrypt
    argument ...TELNET ENCRYPT option.
    
    telnet is weak and insecure.Valid arguments for the encrypt command are:
disable
        type [input|output]encrypt disable ?
          command.enable
        type [input|output]encrypt enable ?
          command.inputencrypt start input
          command.-inputencrypt stop input
          command.outputencrypt start output
          command.-outputencrypt stop output
          command.start
        [input|output]input and output, both
          input and output are enabled. To obtain a list of available types, use
          the encrypt enable ? command.statusstop
        [input|output]type
        typeencrypt start or encrypt
          stop commands.environ
    arguments ...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 valueundefine
        variableexport
        variableunexport
        variablelist* will be sent automatically, other variables
          will only be sent if explicitly requested.?environ
          command.logoutTELNET 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
    typecharacterTELNET LINEMODE option, or, if the
          remote side does not understand the LINEMODE
          option, then enter “character at a time“ mode.lineTELNET LINEMODE option, or, if the
          remote side does not understand the LINEMODE
          option, then attempt to enter “old-line-by-line“
        mode.isig
        (-isig)TRAPSIG mode
          of the LINEMODE option. This requires that the
          LINEMODE option be enabled.edit
        (-edit)EDIT mode of
          the LINEMODE option. This requires that the
          LINEMODE option be enabled.softtabs
        (-softtabs)SOFT_TAB mode
          of the LINEMODE option. This requires that the
          LINEMODE option be enabled.litecho
        (-litecho)LIT_ECHO mode
          of the LINEMODE option. This requires that the
          LINEMODE option be enabled.?mode
          command.open
    host [-l
    user] [-a]
    [[-]port]telnet will attempt to contact a TELNET server at
      the default port. The host specification may be either a host name (see
      hosts(5)) or an Internet
      address specified in the “dot notation” (see
      inet(3)). The
      -l option may be used to specify the user name to
      be passed to the remote system via the ENVIRON
      option. If a port is specified telnet omits any
      automatic initialisation of TELNET options. When the port number is
      preceded by a minus sign, the initial option negotiation is done.
    After establishing a connection, the file
        .telnetrc in the user's home directory is read.
        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 such a line is a string identifying the machine that
        is being connected to. It may be the hostname or numeric address
        specified as the argument host, the canonical name
        of that string as determined by
        getaddrinfo(3), or
        the string “DEFAULT” indicating all hosts. 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.
quittelnet. An
      end of file (in command mode) will also close a session and exit.send
    argumentsabortTELNET ABORT (Abort processes)
          sequence.aoTELNET AO (Abort Output) sequence,
          which should cause the remote system to flush all output
          from the remote system to the
          user's terminal.aytTELNET AYT (Are You There) sequence,
          to which the remote system may or may not choose to respond.brkTELNET BRK (Break) sequence, which
          may have significance to the remote system.ecTELNET EC (Erase Character)
          sequence, which should cause the remote system to erase the last
          character entered.elTELNET EL (Erase Line) sequence,
          which should cause the remote system to erase the line currently being
          entered.eofTELNET EOF (End Of File)
        sequence.eorTELNET EOR (End of Record)
        sequence.escapetelnet escape character
          (initially “^”).gaTELNET GA (Go Ahead) sequence, which
          likely has no significance to the remote system.getstatusTELNET STATUS
          command, getstatus will send the
          subnegotiation to request that the server send its current option
          status.ipTELNET IP (Interrupt Process)
          sequence, which should cause the remote system to abort the currently
          running process.nopTELNET NOP (No OPeration)
        sequence.suspTELNET SUSP (SUSPend process)
          sequence.synchTELNET 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
        cmddont
        cmdwill
        cmdwont
        cmdTELNET 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.?send
          command.set
    argument valueunset
    argument valueset 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 variables 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 variables for the
      toggle command may be explicitly set or unset
      using the set and unset
      commands.
    aytLINEMODE
          is enabled, and the status character is typed, a
          TELNET AYT sequence (see send
          ayt above) is sent to the remote host. The initial value for
          the "Are You There" character is the terminal's status
          character.echoeoftelnet 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.erasetelnet is in
          localchars mode (see
          toggle localchars
          below), and if telnet is
          operating in “character at a time” mode, then when this
          character 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.escapetelnet escape character (initially
          “^[”) which causes entry into
          telnet command mode (when connected to a
          remote system).flushoutputtelnet 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.forw1forw2LINEMODE, 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.interrupttelnet 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.killtelnet is in
          localchars mode (see
          toggle localchars
          below), and if telnet
          is operating in “character at a time” mode, then when
          this character 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.lnexttelnet is operating in
          LINEMODE or “old line by line“
          mode, then this character is taken to be the terminal's
          lnext character. The initial value for the
          lnext character is taken to be the terminal's
          lnext character.quittelnet 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.reprinttelnet is operating in
          LINEMODE or “old line by line“
          mode, then this character is taken to be the terminal's
          reprint character. The initial value for the
          reprint character is taken to be the terminal's
          reprint character.rlogintelnet command. The initial
          state is to disable the rlogin escape character.startTELNET 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 character.stopTELNET 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
          character.susptelnet 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.tracefilenetdata or option
          tracing being TRUE, will be written. If it is
          set to “-”, then tracing
          information will be written to standard output (the default).worderasetelnet 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.?set
          (unset) commands.slc
    stateslc 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.
    checkexporttelnet was started.import?slc
          command.statustelnet. This includes
      the peer one is connected to, as well as the current mode.toggle
    arguments ...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:
    authdebugautoflushautoflush 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 acknowledges (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)).autodecryptTELNET ENCRYPT option is negotiated,
          by default the actual encryption (decryption) of the data stream does
          not start automatically. The autoencrypt (autodecrypt) command states
          that encryption of the output (input) stream should be enabled as soon
          as possible.
        
        telnet is weak and insecure.autologinTELNET
          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 the
          -a option on the open
          command.autosynchautosynch 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.binaryTELNET BINARY option on
          both input and output.inbinaryTELNET BINARY option on
          input.outbinaryTELNET BINARY option on
          output.crlfTRUE, 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.crmodFALSE.debugsuper user). The initial value for this toggle
          is FALSE.encdebuglocalcharsTRUE, 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).netdataFALSE.optionstelnet
          protocol processing (having to do with TELNET options). The initial
          value for this toggle is FALSE.prettydumpnetdata 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
          output, and the beginning of any TELNET escape sequence is preceded by
          a '*' to aid in locating them.skiprcTRUE, 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.termdataFALSE.verbose_encryptverbose_encrypt toggle is
          TRUE, telnet prints
          out a message each time encryption is enabled or disabled. The initial
          value for this toggle is FALSE. Note: Because
          of export controls, data encryption is not supported outside of the
          United States and Canada.?toggle commands.ztelnet. This command only works when the
      user is using the csh(1).!
    [command]?
    [command]telnet prints a help
      summary. If a command is specified, telnet will
      print the help information for just that command.telnet uses at least the HOME,
  SHELL, DISPLAY, and
  TERM environment variables. Other environment
  variables may be propagated to the other side via the TELNET
  ENVIRON option.
telnet command appeared in
  4.2BSD. IPsec support was added by WIDE/KAME project,
  in 1999.
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.
| April 16, 2022 | NetBSD 10.1 |