2.11BSD#431 - /usr/man/cat8/telnetd.0

TELNETD(8)	    UNIX Programmer's Manual	       TELNETD(8)


NAME
     telnetd - DARPA TELNET protocol server

SYNOPSIS
     /usr/libexec/telnetd

DESCRIPTION
     Telnetd is a server which supports the DARPA standard TELNET
     virtual terminal protocol.  Telnetd is invoked by the inter-
     net server (see inetd(8)), normally for requests to connect
     to the TELNET port as indicated by the /etc/services file
     (see services(5)).

     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 pass-
     ing characters between the remote client and the login pro-
     cess.

     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 "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: binary, terminal type, and suppress go ahead.

SEE ALSO
     telnet(1C)

BUGS
     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
     doesn't make use of them.

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

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


Printed 11/24/99	November 16, 1996			1


TELNETD(8)	    UNIX Programmer's Manual	       TELNETD(8)


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

     The packet interface to the pseudo-terminal (see pty(4))
     should be used for more intelligent flushing of input and
     output queues.

     Telnetd never sends TELNET go ahead commands.


Printed 11/24/99	November 16, 1996			2