OSF

NAME

telnetd − The DARPA elnet protocol server

SYNOPSIS

telnetd [−debug [port]] [−D modifier ...]

FLAGS

-debug [port]
Starts telnetd manually, rather than through inetd, on alternate TCP port number port (if specified). 

-D modifier ...
Prints out debugging information.  modifiers are:

optionsPrints information about negotiation of elnet options

reportSame as options with additional processing information

netdataDisplays the data stream received by telnetd

ptydataDisplays data written to the pty

exerciseNot yet implemented

DESCRIPTION

The telnetd daemon is a server that supports the DARPA (Defense Advanced Research Projects Agency) standard elnet virtual terminal protocol.  telnetd is invoked by the Internet server (see inetd(8)) normally for requests to connect to the elnet port as indicated by the /etc/services file (see services(4)).  The −debug flag may be used, to start up telnetd manually.  If started up this way, port may be specified to run telnetd on an alternate TCP port number. 

The −D options may be used for debugging purposes.  This allows telnetd to print out debugging information to the connection, allowing the user to see what telnetd is doing. 

The telnetd daemon operates by allocating a pseudoterminal device (see pty(4)) for a client, then creating a login process that has the slave side of the pseudoterminal as stdin, stdout, and stderr.  telnetd manipulates the master side of the pseudo-terminal, implementing the elnet protocol and passing characters between the remote client and the login process. 

When a elnet session is started up, telnetd sends elnet options to the client side, indicating a willingness to do remote echo of characters, to suppress go ahead, to do remote flow control, and to receive terminal type information, terminal speed information, and window size 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 pseudoterminal allocated to the client is configured to operate in cooked mode, and with XTABS and CRMOD enabled (see tty(4)). 

The telnetd daemon is willing to do: echo, binary, suppress go ahead, and timing mark.  telnetd is willing to have the remote client do: line mode, binary, terminal type, terminal speed, window size, toggle flow control, environment, X display location, and suppress go ahead. 

The telnetd daemon never sends elnet go ahead commands. 

Note that binary mode has no common interpretation except between similar operating systems (Unix compatible systems in this case). 

Note also that the terminal type name received from the remote client is converted to lowercase. 

CAUTIONS

Some telnet commands are only partially implemented. 

Because of bugs in the original 4.2BSD telnet(1), telnetd performs some dubious protocal exchanges to try to discover if the remote client is, in fact, a 4.2BSD telnet(1). 

FILES

/usr/sbin/telnetd
Specifies the command path

RELATED INFORMATION

Commands: telnet(1)