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@(#)telnetd.8 6.1 (Berkeley) 04/27/85

C 5 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 created by telnetd will have debugging enabled (see SO_DEBUG in socket (2)).

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 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 (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.

telnet(1C) A complete list of the options supported should be given here.