RFC 1408 (rfc1408) - Page 2 of 7

Telnet Environment Option

RFC 1408               Telnet Environment Option            January 1993


   IAC DO ENVIRON

      The sender of this command is willing to receive environment
      variables.

   IAC DONT ENVIRON

      The sender of this command refuses to accept environment
      variables.

   IAC SB ENVIRON SEND [ type ... [ type ... [ ... ] ] ] IAC SE

      The sender of this command requests that the remote side send its
      environment variables.  The "type" may be either VAR or USERVAR,
      to indicate either well known or user variable names.  Only the
      side that is DO ENVIRON may initiate a SEND command.  If a list of
      variables is specified, then only those variables should be sent.
      If no list is specified, then the default environment, of both
      well known and user defined variables, should be sent.  If one of
      the variables has no name, then all the variables of that type
      (well known or user defined)  in the default environment should be
      sent.

   IAC SB ENVIRON IS type ... [ VALUE ... ] [ type ... [ VALUE ... ] [

   The sender of this command is sending environment variables.  This
      command is sent in response to a SEND request.  Only the side that
      is WILL ENVIRON may send an IS command.  The "type"/VALUE pairs
      must be returned in the same order as the SEND request specified
      them, and there must be a response for each "type ..." explicitly
      requested.  The "type" will be VAR or USERVAR.  Multiple
      environment variables may be sent.  The characters following a
      "type" up to the next "type" or VALUE specify the variable name.
      The characters following a VALUE up to the next "type" specify the
      value of the variable.  If a "type" is not followed by a VALUE
      (e.g., by another VAR, USERVAR, or IAC SE) then that variable is
      undefined.  If a VALUE is immediately followed by a "type" or IAC,
      then the variable is defined, but has no value.  If an IAC is
      contained between the IS and the IAC SE, it must be sent as IAC
      IAC.  If a variable or a value contains a VAR, it must be sent as
      ESC VAR.

      If a variable or a value contains a USERVAR, it must be sent as
      ESC USERVAR.  If a variable or a value contains a VALUE, it must
      be sent as ESC VALUE.  If a variable or a value contains an ESC,
      it must be sent as ESC ESC.





Telnet Working Group