TELNETD(8)                                             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 TEL-
       NET  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 infor-
       mation  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 dis-
       plays  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 informa-
       tion, terminal speed information, and window size informa-
       tion  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.




                          April 20, 1991                        1

TELNETD(8)                                             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 dis-
       cover if the remote client is, in fact,  a  4.2  BSD  tel-
       net(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.







































                          April 20, 1991                        2