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telnetd(8)							   telnetd(8)



NAME

  telnetd - The	DARPA telnet protocol server

SYNOPSIS

  telnetd [-debug | debug6 [port]] [-D modifier...]

OPTIONS

  -debug|debug6	[port]
      Starts telnetd manually, rather than through inetd, on alternate TCP
      port number port (if specified). It either creates an IPv4 socket
      (-debug) or IPv6 socket (-debug6).

  -D modifier ...
      Prints out debugging information.	 Valid values for modifier are:

      options Prints information about negotiation of telnet options.

      report  Prints the same information as options, along with additional
	      processing information.

      netdata Displays the data	stream received	by telnetd.

      ptydata Displays data written to the pty.

      exercise
	      Not yet implemented.

DESCRIPTION

  The telnetd daemon is	a server that supports the DARPA (Defense Advanced
  Research Projects Agency) standard telnet virtual terminal protocol. The
  telnetd daemon is invoked by the Internet server (see	inetd(8)) normally
  for requests to connect to the telnet	port as	indicated by the
  /etc/services	file (see services(4)).	Either the -debug option (for IPv4
  sockets) or -debug6 option (for IPv6 sockets)	may be used, to	start up tel-
  netd manually.  If the daemon	is started up this way,	port may be specified
  to run telnetd on an alternate TCP port number.

  The -D options argument 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(7)) for a	client,	then creating a	login process that has the slave side
  of the pseudoterminal	as stdin, stdout, and stderr.  The telnetd daemon
  manipulates the master side of the pseudo-terminal, implementing the telnet
  protocol and passing characters between the remote client and	the login
  process.


  When a telnet	session	is started up, telnetd sends telnet 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(7)).

  The telnetd daemon is	willing	to do: echo, binary, suppress go ahead,	and
  timing mark.	The telnetd daemon 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 telnet	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.

  The telnet command uses the default Type-of-Service value recommended	by
  RFC1060, which is as follows:

  telnet
      Low delay

  You can configure this value by specifying it	in the /etc/iptos file.	For
  more information, see	iptos(4).

  By default, the telnetd daemon starts	the login dialog using the login
  string specified in the message field	of the /etc/gettydefs file. If you
  want to use a	customized banner, create an /etc/issue.net or /etc/issue
  file.	The telnetd daemon reads the file that exists and writes its contents
  over a new telnet connection prior to	starting the login dialog. If both
  files	exist, only the	/etc/issue.net file is used.

CAUTIONS

  Some telnet commands are only	partially implemented.

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

FILES

  /usr/sbin/telnetd
      Specifies	the command path.

  /etc/issue.net
      Specifies	the path name for the network issue identification file.

  /etc/issue
      Specifies	the path name for the issue identification file.

SEE ALSO

  Commands: telnet(1)

  Files: iptos(4), issue(4), issue.net(4)