TELNETD(8)						      System Manager'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 internet 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 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  charac-
       ters,  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, ter-
       minal 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).

       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.

4.2 Berkeley Distribution					 November 16, 1996							TELNETD(8)