RFC 438 (rfc438) - Page 3 of 3

FTP server-server interaction

RFC 438              FTP Server-Server Interaction          January 1973


      1. On success the reply must be the 255 FTP server data socket
         reply; that is, the 255 reply can not be deferred until receipt
         of a data transfer command.  (This is to allow the user to
         transmit the server's response to the program at the third
         site; see the example below.)

      2. After a LSTN command the SOCK command is to be interpreted by
         the server as specification of the acceptable RFC for
         subsequent data transfer command that use the allocated socket.

   With this extension to FTP, the RSEXEC program could accomplish the
   APPEND in the example above as follows:

        to SITE1:                       to SITE2:

           .                                .
           .                                .
           .                                .

   1.                                   LSTN R CRLF
                                        (let X = socket
                                         allocated)

   2.   SOCK SITE2,X CRLF
        (let Y = socket in 255
         reply from SITE1)

   3.                                   SOCK SITE1,Y CRLF

   4.  RETR PROG1.PL1                   APPE PROG2.Pl1 CRLF

          .                                 .
          .                                 .
          .                                 .


   In closing it is appropriate to note that an experimental RSEXEC
   program of the sort suggested above has been operational on TENEXs
   for about 8 months.  It currently uses a private, resource sharing
   protocol (RSP) that includes file transfer operations.  RSP supports
   server-server cooperation; in RSP data connections are established in
   a symmetric way (alternative 1 above).


         [ This RFC was put into machine readable form for entry ]
         [ into the online RFC archives by Mirsad Todorovac 5/98 ]





Thomas, et. al.