TELNETD(8C)TELNETD(8C)NAME
telnetd - DARPA TELNET protocol server
SYNOPSIS
/usr/etc/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
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 ALSOtelnet(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.
There can be a loss of characters or improper handling of special
characters (e.g., carriage returns and line feeds) during a telnet
session from a local non-NEXTSTEP host to a remote NEXTSTEP host. This
can be fixed by using the stty -extproc on the remote NEXTSTEP host
you're logged into (either from the command line or adding it to your
.login file). This causes characters to be processed external to the
terminal driver.
4.2 Berkeley Distribution May 28, 1986 TELNETD(8C)