RFC 857 (rfc857) - Page 2 of 5


Telnet Echo Option



Alternative Format: Original Text Document





RFC 857                                                         May 1983


   The NVT has a printer and a keyboard which are nominally
   interconnected so that "echoes" need never traverse the network; that
   is to say, the NVT nominally operates in a mode where characters
   typed on the keyboard are (by some means) locally turned around and
   printed on the printer.  In highly interactive situations it is
   appropriate for the remote process (command language interpreter,
   etc.) to which the characters are being sent to control the way they
   are echoed on the printer.  In order to support such interactive
   situations, it is necessary that there be a TELNET option to allow
   the parties at the two ends of the TELNET connection to agree that
   characters typed on an NVT keyboard are to be echoed by the party at
   the other end of the TELNET connection.

5. Description of the Option

   When the echoing option is in effect, the party at the end performing
   the echoing is expected to transmit (echo) data characters it
   receives back to the sender of the data characters.  The option does
   not require that the characters echoed be exactly the characters
   received (for example, a number of systems echo the ASCII ESC
   character with something other than the ESC character).  When the
   echoing option is not in effect, the receiver of data characters
   should not echo them back to the sender; this, of course, does not
   prevent the receiver from responding to data characters received.

   The normal TELNET connection is two way.  That is, data flows in each
   direction on the connection independently; and neither, either, or
   both directions may be operating simultaneously in echo mode.  There
   are five reasonable modes of operation for echoing on a connection
   pair:

      
                
                 Neither end echoes

      
                
             One end echoes for itself






Postel & Reynolds