telnetd - DARPA TELNET protocol server
/etc/telnetd [ -d ] [ port ]
Telnetd is a server which supports the DARPA standard TELNET virtual
terminal protocol. The TELNET server operates at the port indicated in
the ``telnet'' service description; see services(5). This port number
may be overridden (for debugging purposes) by specifying a port number
on the command line. If the -d option is specified, each socket cre-
ated by telnetd will have debugging enabled (see SO_DEBUG in
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 proto-
col and passing characters between the client and login process.
When a TELNET session is started up, telnetd sends a TELNET option to
the client side indicating a willingness to do ``remote echo'' of char-
acters. The pseudo terminal allocated to the client is configured to
operate in ``cooked'' mode, and with XTABS and CRMOD enabled (see
tty(4)). Aside from this initial setup, the only mode changes telnetd
will carry out are those required for echoing characters at the client
side of the connection.
Telnetd supports binary mode, and most of the common TELNET options,
but does not, for instance, support timing marks. Consult the source
code for an exact list of which options are not implemented.
A complete list of the options supported should be given here.
4th Berkeley Distribution 4 March 1983 TELNETD(8C)