# 2.11BSD#431 - /usr/man/cat1/telnet.0

    TELNET(1C)	    UNIX Programmer's Manual	       TELNET(1C)

    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 immedi-
         ately 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

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    TELNET(1C)	    UNIX Programmer's Manual	       TELNET(1C)

    	  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 char-
    	  acter (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 sum-
    	  mary.  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 (ini-
    	       tially "^]").

    	  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

    Printed 11/26/99	  May 10, 1986				2

    TELNET(1C)	    UNIX Programmer's Manual	       TELNET(1C)

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

    	  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

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    TELNET(1C)	    UNIX Programmer's Manual	       TELNET(1C)

    	       "line by line" mode, toggles between doing local
    	       echoing of entered characters (for normal process-
    	       ing), and suppressing echoing of entered charac-
    	       ters (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 local-
    	       chars 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 local-
    	       chars 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 local-
    	       chars 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 local-
    	       chars below), and if telnet is operating in "char-
    	       acter 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 local-
    	       chars below), and if telnet is operating in "char-
    	       acter 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.

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    TELNET(1C)	    UNIX Programmer's Manual	       TELNET(1C)

    	  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 char-
    	       acter is taken to be the terminal's eof character.

         toggle arguments...
    	  Toggle (between TRUE and FALSE) various flags that con-
    	  trol 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 (hope-
    	       fully) 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 recog-
    	       nized (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

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    TELNET(1C)	    UNIX Programmer's Manual	       TELNET(1C)

    	       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 proto-
    	       col processing (having to do with TELNET options).
    	       The initial value for this toggle is FALSE.

    	  netdata
    	       Toggles the display of all network data (in hexa-
    	       decimal format).  The initial value for this tog-
    	       gle 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.

    Printed 11/26/99	  May 10, 1986				6

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