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 a connection request on the port indicated in the telnet service description.

The telnetd server operates by allocating a pseudo-terminal device 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, 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.

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, suppress go ahead, echo, and timing mark. It also allows a remote client to do binary, terminal type, and suppress go ahead.

RESTRICTIONS

Some TELNET commands are only partially implemented. 

The TELNET protocol allows the exchange of the number of lines and columns on the user’s terminal, but telnetd does not make use of them.

The terminal type name received from the remote client is converted to lower case. 

The telnetd server never sends TELNET go ahead commands.

SEE ALSO

telnet(1c), pty(4), tty(4), services(5), inetd(8c)

Maintenance