# telnet(1)

    NAME
         telnet - user interface to the TELNET protocol

    SYNOPSIS
         telnet [ host [ port ] ]

    DESCRIPTION
         Telnet is  used  to  communicate  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  an  input  mode.   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 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).

         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 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.

         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
              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))  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 end of  file  (in
              command mode) will also close a session and exit.

         z
              Suspend telnet.  This command only works when the user is using  the
              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
              permission 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... ]
              Displays 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
              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):

         escape
              Sends the current telnet escape character (initially "^]").

         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  4.2 BSD system -- if it doesn't work, a lower
              case "r" may be echoed on the terminal).

         brk
              Sends the TELNET BRK (Break) sequence, which may  have  significance
              to the remote system.

         ip
              Sends 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 character 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 suppressing 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 connected 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 specified.
              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 toggle is TRUE in "line by line" mode, and FALSE in  "character
              at a time" mode.

         autoflush
              If autoflush and localchars are both TRUE, then when the  ao,  intr,
              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)).

         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 carriage return  mode.   When  this  mode  is  enabled,  most
              carriage  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 superuser).   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.

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

         ?
              Displays the legal toggle commands.

    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.