telnetd(8c)
NAME
telnetd − DARPA TELNET protocol server
SYNTAX
/etc/telnetd
DESCRIPTION
The telnetd server supports the DARPA standard TELNET virtual terminal protocol. The TELNET server is invoked when inetd(receives)receives the port indicated in the “telnet” service description; see services(.).
The telnetd server operates by allocating a pseudo-terminal device (see pty() ) for a client, then creating a login process which has the slave side of the pseudo-terminal as stdin, stdout, and stderr. The telnetd server manipulates the master side of the pseudo terminal, implementing the TELNET protocol 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 characters. The pseudo terminal allocated to the client is configured to operate in “cooked” mode, and with XTABS and CRMOD enabled. For further information, 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.
The telnetd server supports binary mode, and most of the common TELNET options, but does not, for instance, support timing marks.