NAME

telnetd - DARPA TELNET protocol server

SYNOPSIS

/etc/telnetd [ −d ] [ port ]

DESCRIPTION

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.  This port number may be overridden (for debugging purposes) by specifying a port number in the command line.  If the -d option is specified, telnetd creates sockets with debugging enabled (see SO_DEBUG in socket(3N)).

telnetd operates by allocating a pseudo-terminal device (see pty(7)) for a client, then creating a login process where the slave side of the pseudo-terminal is stdin, stdout, and stderr. Telnetd also changes the master side of the pseudo terminal by implementing the TELNET protocol and passing characters between the client and login process. 

When a TELNET session starts, telnetd sends a TELNET option to the client side indicating a willingness to "remotely echo" characters.  The client’s pseudo terminal is configured for "cooked" mode, with XTABS and CRMOD enabled (see tty(4)). Aside from this initial setup, telnetd only changes the modes required for echoing characters at the client’s side. 

Telnetd supports binary mode, and most of the common TELNET options.  Consult the source code for an exact list of which options are not implemented. 

SEE ALSO

telnet(1C)

Version 2.3  —  July 04, 1985