TELNETD(ADMN)                      UNIX System V



     Name
          telnetd - DARPA TELNET protocol server


     Syntax
          /etc/telnetd


     Description
          telnetd is a server that supports the DARPA standard  TELNET
          virtual  terminal  protocol.   telnetd  is  invoked  by  the
          internet server (see inetd(ADMN)), normally for requests  to
          connect to the TELNET port as indicated by the /etc/services
          file (see services(SFF)).

          telnetd operates by allocating a pseudo-terminal device  for
          a  client,  then creating a login process that 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,  and  to
          receive  terminal  type  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  ICANON  mode,  and with TAB3 and ICRNL enabled.
          (See termio(M).)

          telnetd is willing to do: echo, binary, suppress  go  ahead,
          and  timing  mark.   telnetd  is  willing to have the remote
          client do: binary, terminal type, and suppress go ahead.


     See Also
          telnet(TC)


     Notes
          Some TELNET commands are only partially implemented.

          The TELNET protocol allows for the exchange of the number of
          lines  and  columns on the user's terminal, but telnetd does
          not make use of them.

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

          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 lowercase.

          The packet  interface  to  the  pseudo  terminal  should  be
          implemented  for  intelligent  flushing  of input and output
          queues.

          telnetd never sends TELNET go ahead commands.


     (printed 8/17/89)                          TELNETD(ADMN)