telnetd(1M)                                                        telnetd(1M)


NAME
     telnetd - internet TELNET protocol server

SYNOPSIS
     /usr/etc/telnetd [ -h ] [ -n ]

DESCRIPTION
     telnetd is a server which supports the Internet standard TELNET virtual
     terminal protocol.  telnetd is invoked by the Internet super-server (see
     inetd(1M)), normally for requests to connect to the TELNET port as
     indicated by the /etc/services file (see services(4)).

     If the file /etc/issue.net exists, its contents will be displayed before
     the login prompt in place of the default host information banner.  The -h
     option suppresses the host information and /etc/issue.net banner before
     the login prompt.

     The -n option suppresses transport-level keep-alive messages.  The use of
     keep-alive messages allows sessions to be timed out if the client crashes
     or becomes unreachable.

     telnetd operates by allocating a pseudo-terminal device (see pty(7)) 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 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.

     telnetd is willing to do:  echo, binary, suppress go ahead, and timing
     mark.  telnetd is willing to have the remote client do:  binary, terminal
     type, terminal speed, window size, toggle flow control, environment, X
     display location, and suppress go ahead.  Attempts to set environment
     variables understood by rld(1) are ignored and logged.  Currently, these
     are LD_LIBRARY_PATH and any variable name starting with _RLD.

NOTES
     The /etc/issue.net file may contain \h or %h sequences which will be
     interpreted by telnetd and cause it to display the hostname of the
     system.

FILES
     /etc/issue.net - message displayed before login prompt


SEE ALSO
     telnet(1C).

BUGS
     Some TELNET commands are only partially implemented.

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

     Binary mode has no common interpretation except between similar operating
     systems (UNIX in this case).

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

     telnetd never sends TELNET go ahead commands.


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