TELNETD(8)                     1991                    TELNETD(8)


NAME
       telnetd - DARPA TELNET protocol server

SYNOPSIS
       /etc/telnetd [-debug [port]] [-l] [-D options] [-D report]
       [-D exercise] [-D netdata] [-D ptydata]

DESCRIPTION
       Telnetd is a server  which  supports  the  DARPA  standard
       TELNET  virtual  terminal protocol.  Telnetd is invoked by
       the internet server (see inetd(8)), normally for  requests
       to  connect  to  the  TELNET  port  as  indicated  by  the
       /etc/services file (see services(5)).  If the  -debug  may
       be  used, to start up telnetd manually, instead of through
       inetd(8).  If started up this way, port may  be  specified
       to run telnetd on an alternate TCP port number.

       The  -D  option  may be used for debugging purposes.  This
       allows telnet to print out debugging  information  to  the
       connection,  allowing  the  user  to  see  what telnetd is
       doing.   There  are  several  modifiers:  options   prints
       information  about  the  negotiation  of  TELNET  options,
       report  prints  the   options   information,   plus   some
       additional  information about what processing is going on,
       netdata displays the  data  stream  received  by  telnetd,
       ptydata displays data written to the pty, and exercise has
       not been implemented yet.

       Telnetd operates by allocating  a  pseudo-terminal  device
       (see  pty(4))  for a client, then creating a login process
       which has the slave side of the pseudo-terminal as  stdin,
       stdout,  and  stderr.  Telnetd manipulates the master side
       of the pseudo-terminal, implementing the  TELNET  protocol
       and  passing  characters between the remote client and the
       login process.

       When a TELNET session is started up, telnetd sends  TELNET
       options  to the client side indicating a willingness to do
       remote echo of characters, to suppress  go  ahead,  to  do
       remote   flow   control,  and  to  receive  terminal  type
       information, terminal speed information, and  window  size
       information  from the remote client.  If the remote client
       is willing, the remote terminal type is propagated in  the
       environment  of  the  created  login process.  The pseudo-
       terminal allocated to the client is configured to  operate
       in  cooked  mode,  and  with  XTABS and CRMOD enabled (see
       tty(4)).

       Telnetd is willing to do: echo, binary, suppress go ahead,
       and  timing  mark.   Telnetd is willing to have the remote
       client  do:  linemode,  binary,  terminal  type,  terminal
       speed,  window  size,  toggle flow control, environment, X
       display location, and suppress go ahead.




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TELNETD(8)                     1991                    TELNETD(8)


SEE ALSO
       telnet(1)

BUGS
       Some TELNET commands are only partially implemented.

       Because of bugs in the original 4.2 BSD telnet(1), telnetd
       performs   some  dubious  protocol  exchanges  to  try  to
       discover if the remote client  is,  in  fact,  a  4.2  BSD
       telnet(1).

       Binary  mode  has  no common interpretation except between
       similar operating systems (Unix in this case).

       The terminal type name received from the remote client  is
       converted to lower case.

       Telnetd never sends TELNET go ahead commands.







































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