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TELNET(1C)                                                          TELNET(1C)



NAME
       telnet - user interface to a remote system using the TELNET protocol

SYNOPSIS
       telnet [ host [ port ] ]

AVAILABILITY
       This  command  is  available  with the Networking software installation
       option.  Refer to for information on how to install optional software.

DESCRIPTION
       telnet communicates with another host using the  TELNET  protocol.   If
       telnet  is invoked without arguments, 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 (see below) with those arguments.

       Once a connection has been opened, telnet enters input mode.   In  this
       mode,  text  typed  is sent to the remote host.  The input mode entered
       will be either "character at a time" or "line  by  line"  depending  on
       what the remote system supports.

       In  "character  at a time" mode, most text typed is immediately sent to
       the remote host for processing.

       In "line by line" mode, all text is echoed locally, and (normally) only
       completed  lines  are sent to the remote host.  The "local echo charac-
       ter" (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).

       In either mode, if the localchars toggle is TRUE (the default  in  line
       mode;  see  below),  the  user's  quit,  intr, and flush characters are
       trapped locally, and sent as TELNET protocol sequences  to  the  remote
       side.   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 `^]', (control-right-
       bracket)).  When in command mode, the normal terminal  editing  conven-
       tions are available.

USAGE
   Telnet Commands
       The  following  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, and display commands).

       open host [ port ]
              Open a connection to the named host.  If no port number is spec-
              ified, 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(3N)).

       close  Close a TELNET session and return to command mode.

       quit   Close  any open TELNET session and exit telnet.  An EOF (in com-
              mand mode) will also close a session and exit.

       z      Suspend telnet.  This command only works when the user is  using
              a shell that supports job control, such as csh(1).

       mode type
              type  is either line (for "line by line" mode) or character (for
              "character at a time" mode).  The remote host is asked for  per-
              mission  to  go  into the requested mode.  If the remote host is
              capable of entering  that  mode,  the  requested  mode  will  be
              entered.

       status Show  the  current status of telnet.  This includes the peer one
              is connected to, as well as the current mode.

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

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

       send arguments
              Send 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):

              escape Send  the  current  telnet  escape  character  (initially
                     `^]').

              synch  Send 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 4.2  BSD
                     system  --  if  it does not work, a lower case "r" may be
                     echoed on the terminal).

              brk    Send the TELNET BRK (Break) sequence, which may have sig-
                     nificance to the remote system.

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

              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.

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

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

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

              nop    Sends the TELNET NOP (No Operation) sequence.

              ?      Prints out help information for the send command.

       set argument value
              Set any one of a number of telnet variables to a specific value.
              The special value "off" turns off the function  associated  with
              the  variable.  The values of variables may be interrogated with
              the display command.  The variables which may be specified are:

              echo   This is the value (initially `^E') which, when  in  "line
                     by  line"  mode,  toggles  between doing local echoing of
                     entered characters (for normal processing), and suppress-
                     ing  echoing  of entered characters (for entering, say, a
                     password).

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

              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.

              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.

              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.

              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 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.

              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 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.

              eof    If telnet is operating in "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.

       toggle arguments...
              Toggle (between TRUE and FALSE) various flags that  control  how
              telnet responds to events.  More than one argument may be speci-
              fied.  The state of these flags may  be  interrogated  with  the
              display command.  Valid arguments are:

              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 tog-
                     gle is TRUE in "line by line" mode, and FALSE in "charac-
                     ter at a time" mode.

              autoflush
                     If  autoflush and localchars are both TRUE, then when the
                     ao, intr, or quit characters are recognized  (and  trans-
                     formed 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",  other-
                     wise FALSE (see stty(1V)).

              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.

              crmod  Toggle  RETURN  mode.   When  this  mode is enabled, most
                     RETURN characters received from the remote host  will  be
                     mapped  into  a RETURN followed by a LINEFEED.  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 RETURN, but
                     never  LINEFEED.   The  initial  value for this toggle is
                     FALSE.

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

              options
                     Toggle  the display of some internal telnet protocol pro-
                     cessing (having to do with TELNET options).  The  initial
                     value for this toggle is FALSE.

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

              ?      Display the legal toggle commands.

SEE ALSO
       csh(1), rlogin(1C), stty(1V) inet(3N), hosts(5)

BUGS
       There is no adequate way for dealing with flow control.

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

       There is enough settable state to justify a .telnetrc file.

       No capability for a .telnetrc file is provided.

       In "line by line" mode, the terminal's EOF character is only recognized
       (and sent to the remote system) when it is the  first  character  on  a
       line.



                               17 December 1987                     TELNET(1C)