NWG/RFC# 737                                         KLH 31 Oct 77 42217
Network Working Group                                     K. Harrenstien
Request for Comments: 737                                         SRI-KL
NIC: 42217                                               31 October 1977



                          FTP Extension: XSEN




This note describes an extension to the File Transfer Protocol which
provides for "sending" a message to a logged-in user, as well as
variants for mailing it normally whether the user is logged in or not.

Several systems have a SEND command or program which sends a message
directly to a user's terminal.   On the SAIL (SU-AI) and ITS
(MIT-(AI/ML/MC/DMS)) systems the concept has been broadened to allow
SEND'ing to users on other network sites; to support this, three new FTP
commands were added which have a syntax identical to the existing MAIL
command.  For reference, the latter is:

   MAIL <SP> <recipient name> <CRLF>

      If accepted, returns 350 reply and considers all succeeding lines
      to be the message text, terminated by a line containing only a
      period, upon which a 256 completion reply is returned.  Various
      errors are possible.

The new commands, with their special replies, are:

   XSEN -- Send to terminal.

      Returns 453 failure reply if the addressee is refusing or not
      logged in.

   XSEM -- Send, Mail if can't.

      Returns 009 notification reply if message cannot be SENT.

   XMAS -- Mail And Send. (couldn't resist this one)

      No special replies.

Note that for XSEM and XMAS, it is the mailing which determines success,
not the SENDing, although XSEM as implemented uses a 009 reply (in
addition to the normal success/failure code) to indicate that because
the SEND failed, an attempt is being made to mail the message instead.
There are no corresponding variants for MLFL, since messages transmitted
in this way are generally short, and neither I nor Brian Harvey
(implementing respectively the ITS and SAIL servers) wanted to bother.