rfc772.txt

RFC 相关的技术文档

               QUIT
                  221
            INFORMATIONAL COMMANDS
               HELP
                  211, 214
                  500, 501, 502, 421
            MISCELLANEOUS COMMANDS
               NOOP
                  200
                  500 421

STATE DIAGRAMS

   Here we present state diagrams for a very simple minded MTP
   implementation.  Only the first digit of the reply codes is used.
   There is one state diagram for each group of MTP commands.

   The command groupings were determined by constructing a model for
   each command and then collecting together the commands with
   structurally identical models.

   For each command there are three possible outcomes:  "success" (S),
   "failure" (F), and "error" (E). In the state diagrams below we use
   the symbol B for "begin", and the symbol W for "wait for reply".
















                                   24


                                                                        
RFC 772                                                   September 1980
                                                  Mail Transfer Protocol



   We first present the diagram that represents the most MTP commands:

      
                               1,3    +---+
                          ----------->| E |
                         |            +---+
                         |
      +---+    cmd    +---+    2      +---+
      | B |---------->| W |---------->| S |
      +---+           +---+           +---+
                         |
                         |     4,5    +---+
                          ----------->| F |
                                      +---+
      

      This diagram models the commands:

         HELP, MRCP, MRSQ, NOOP, QUIT.






























                                   25


                                                                        
September 1980                                                   RFC 772
Mail Transfer Protocol                                                  



   A more complex diagram models the MAIL command:

      
                   ----  1
                  |    |
      +---+  cmd   -->+---+     2     +---+
      | B |---------->| W |---------->| E |
      +---+           +---+        -->+---+
                       | |        |
                3      | | 4,5    |
         --------------  ------   |
        |                      |  |   +---+
        |               ------------->| S |
        |              |   1,3 |  |   +---+
        |             2|  --------
        |              | |     |
        V              | |     |
      +---+   text    +---+ 4,5 ----->+---+
      |   |---------->| W |---------->| F |
      +---+           +---+           +---+
      

      Note that the "text" here is a series of lines sent from the
      sender to the receiver with no response expected until the last
      line is sent.  (The last line must consist of only a single
      period.)























                                   26


                                                                        
RFC 772                                                   September 1980
                                                  Mail Transfer Protocol



   Finally we present a generalized diagram that could be used to model
   the command and reply interchange:

      
               ------------------------------------
              |                                    |
      Begin   |                                    |
        |     V                                    |
        |   +---+  cmd   +---+ 2         +---+     |
         -->|   |------->|   |---------->|   |     |
            |   |        | W |           | S |-----|
         -->|   |     -->|   |-----      |   |     |
        |   +---+    |   +---+ 4,5 |     +---+     |
        |     |      |    | |      |               |
        |     |      |   1| |3     |     +---+     |
        |     |      |    | |      |     |   |     |
        |     |       ----  |       ---->| F |-----
        |     |             |            |   |
        |     |             |            +---+
         -------------------
              |
              |
              V
             End

























                                   27


                                                                        
September 1980                                                   RFC 772
Mail Transfer Protocol                                                  



CONNECTION ESTABLISHMENT

   The MTP control connection is established via TCP/NCP between the
   receiver process port/socket L and the sender process port/socket U.
   This protocol is assigned the service port/socket 57 (71 octal), that
   is L=57.











































                                   28


                                                                        
RFC 772                                                   September 1980
                                                  Mail Transfer Protocol



APPENDIX A

                  Example of MRSQ R (Recipients-first)

   This is an example of how MRSQ R is used.  First the sender must
   establish that the receiver in fact implements MRSQ.

      S: MRSQ <CRLF>
      R: 200 OK, no scheme selected

   An MRSQ with a null argument always returns a 200 if implemented,
   selecting the default "scheme", i.e., none of them.  If MRSQ were not
   implemented, a code of 4xx or 5xx would be returned.

      S: MRSQ R <CRLF>
      R: 200 OK, using that scheme

   All is well; now the recipients can be specified.

      S: MRCP TO:<Foo@Y> <CRLF>
      R: 200 OK

      S: MRCP TO:<Raboof@Y> <CRLF>
      R: 553  No such user here

      S: MRCP TO:<bar@Y> <CRLF>
      R: 200 OK

      S: MRCP TO:<@Y,@X,fubar@Z> <CRLF>
      R: 200 OK

   Note that the failure of "Raboof" has no effect on the storage of
   mail for "Foo", "bar" or the mail to be forwarded to "fubar@Z"
   through host "X".  Now the message text is furnished, by giving a
   MAIL command with no "TO" argument.

      S: MAIL FROM:<waldo@A><CRLF>
      R: 354 Type mail, ended by <CRLF>.<CRLF>
      S: Blah blah blah blah....etc. etc. etc.
      S: <CRLF>.<CRLF>
      R: 250 Mail sent

   The mail text has now been sent to "Foo" and "bar" as well as
   forwarded to "fubar@Z".





                                   29


                                                                        
September 1980                                                   RFC 772
Mail Transfer Protocol                                                  



APPENDIX B

                     Example of MRSQ T (Text-first)

   Using the same message as the previous example to establish that the
   receiver implements MRSQ.

      S: MRSQ ? <CRLF>
      R: 215 T Text first, please

   MRSQ is indeed implemented, and the receiver says that it prefers
   "T", but that needn't stop the sender from trying something else.

      S: MRSQ R <CRLF>
      R: 501 Sorry, I really can't do that

   It's possible that it could have understood "R" also, but in general
   it's best to use the "preferred" scheme, since the receiver knows
   which is most efficient for its particular site.

      S: MRSQ T <CRLF>
      R: 200 OK, using that scheme

   Scheme "T" is now selected, and the message text is sent by giving a
   mail command with no "TO" argument.

      S: MAIL FROM:<WALDO@A><CRLF>
      R: 354 Type mail, ended by <CRLF>.<CRLF>
      S: Blah blah blah blah....etc. etc. etc.
      S: <CRLF>.<CRLF>
      R: 250 Mail stored

   Now recipients can be specified.

      S: MRCP TO:<Foo@Y> <CRLF>
      R: 250 Stored mail sent

      S: MRCP TO:<Raboof@Y> <CRLF>
      R: 553  No such user here

      S: MRCP TO:<bar@Y> <CRLF>
      R: 250 Stored mail sent

      S: MRCP TO:<@Y,@X,fubar@Z> <CRLF>
      R: 200 OK




                                   30


                                                                        
RFC 772                                                   September 1980
                                                  Mail Transfer Protocol



   The text has now been sent to "Foo" and "bar" at host "Y" and will be
   forwarded to "fubar@Z" through host "X", and still remains stored.  A
   new message can be sent with another MAIL/MRCP ... sequence, but a
   careful sender would reset the state using the exchange below.

      S: MRSQ ? <CRLF>
      R: 215 T Text first, please

   Which resets the state without altering the scheme in effect.








































                                   31