RFC 1097 (rfc1097) - Page 2 of 3

Telnet subliminal-message option

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RFC 1097                       SUBLIMINAL                   1 April 1989


      implementation dependent.

      The first 16-bit value specifies the duration of the message in
      milliseconds.  It is sent MSB first.  The second 16-bit value
      specifies the frequency with which the message is displayed.  It
      represents the number of seconds between displays and is also sent
      MSB first.  The final parameter is the message itself.

      The syntax for this subnegotiation is:

                IAC SB SUBLIMINAL-MESSAGE
                    DURATION[1] DURATION[0]
                    FREQUENCY[1] FREQUENCY[0]
                    MESSAGE_STRING
                IAC SE

      As required by the Telnet protocol, any occurence of 255 in the
      subnegotiation must be doubled to destinguish it from the IAC
      character (which has a value of 255).

3.  Default.

   WONT SUBLIMINAL-MESSAGE

   DONT SUBLIMINAL-MESSAGE

   i.e., subliminal messages will not be displayed.

4.  Motivation for the option

   Frequently the use of "Message of the day" banners and newsletters is
   insufficient to convince stubborn users to upgrade to the latest
   version of telnet.  Some users will use the same outdated version for
   years.  I ran across this problem trying to convince people to use
   the REMOTE-FLOW-CONTROL Telnet option.  These users need to be gently
   "persuaded".

5.  Description and implementation notes.

   The quality of the client implementation will depend on it's ability
   to display and erase text strings in a small amount of time.  The
   current implementation at CMU takes into acount terminal line speed,
   advanced video capabilities, and screen phospher persistance when
   calculating how long to wait before erasing a message.

   While it is permitted for the client to display the message text
   "in-line", best results at obtained by printing the message at the
   top or side of console screen where it will just catch the corner of



Miller
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