rfc726.txt

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           using host is allowed to send a character a time,
           though this would be a waste of RCTE. The
           transmission classes commands are GUIDELINES, so
           deviating from them, as when the user's buffer gets
           full, is allowed.                                        6d4a

           Additionally, the using host may send a break class
           character, without knowing that it is one (as with
           type-ahead).                                             6d4b

             If the user implementation is clever it may send
             the user entered data to the server before it is
             actually needed. This type ahead data may contain
             break characters.




                                                               [page 11]

     NWG/RFC# 726                          JBP DHC 8-MAR-77 08:29  39237
     Remote Controlled Transmission & Echoing Telnet Option



             Assume that only space is a break character (that
             is the last break reset command specified print up
             to and including the break characters and set the
             break classes to class 9). Suppose the user had
             typed "abc<space>def<esc>ghi<cr>". The user side
             RCTE could send it all to the server, but it could
             print only "abc<space>", and would have to buffer
             "def<esc>ghi<cr>" at least until a break reset
             command was received from the server. That break
             reset command could change the break ckasses
             requiring rescanning the buffered string.

             For example suppose the break reset command set the
             break characters to class 5 and the action to print
             up to but not including the break character. The
             user RCTE could then print "def" and discard the
             <esc>, but whould have to continue to buffer the
             "ghi<cr>".

           The problem with buffering occurs when printing on
           the user's terminal must be suspended, after the user
           has typed a currently valid break character and until
           a break reset command is received from the serving
           host. During this time, the user may be typing
           merrily along. The text being typed may be SENT, but
           may not yet be PRINTED.                                  6d4c

           The more common problem of filling the transmission
           buffer, while awaiting a host to host allocate from
           the serving host, may also occur, but this problem is
           well known to implementors and in no way special to
           RCTE.                                                    6d4d

           In any case, when the buffer does fill and further
           text typed by the user will be lost, the user should
           be notified (perhaps by ringing the terminal bell).      6d4e

         Text should be buffered by the using host until the
         user types a character which belongs to the
         transmission class in force at the moment the character
         is typed.                                                   6d5

         Transmission class reset commands may be sent by the
         serving host at any time. If they are frequently sent
         separate from break class reset commands, it will
         probably be better to exit from RCTE and enter regular
         character at a time transmission.                           6d6

         It is not immediately clear what the using host should



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     NWG/RFC# 726                          JBP DHC 8-MAR-77 08:29  39237
     Remote Controlled Transmission & Echoing Telnet Option



         do with currently buffered text, when a transmission
         classes reset command is received. The buffering is
         according to the previous transmission classes scheme.      6d7

           The using host clearly should not simply wait until a
           transmission character (according to the new scheme)
           is typed.                                                6d7a

           Either the buffered text should be rescanned, under
           the new scheme;                                          6d7b

           Or the buffered text should simply be sent as a
           group. This is the simpler approach, and probably
           quite adequate.                                          6d7c

         It is possible to define NO BREAK CHARACTERS except
         Telnet commands (IAC ...). This seems undesirable and
         should not be done.                                         6d8

           If this situation were to occur the using host should
           send a Telnet command to allow the server to know
           when he may reset the break classes, but the
           mechanism is awkward and this case should be avoided.    6d8a

     6.  Sample Interaction:                                           7

       "S:" is sent from serving (WILL RCTE) host to using host.
       "U:" is sent from using (DO RCTE) host to serving host.
       "T:" is entered by the terminal user.
       "P:" is printed on the terminal.
       
       Text surrounded by square brackets ([]) is commentary.
       Text surrounded by angle brackets (<>) is to be taken as
       a single unit. E.g., carriage return is <cr>, and the
       decimal value 27 is represented <27>.                          7a

       The following interaction shows a logon to a Tenex,
       initiation of the DED editor, insertion of some text and
       the return to the Exec level.                                  7b

         An attempt has been made to give some flavor of the
         asynchrony of network I/O and the user's terminal
         input. Many other possible combinations, using the same
         set of actions listed below, could be devised. The
         actual order of events will depend upon network and
         hosts' load and the user's typing speed.                    7b1

       We assume that the user's Telnet is also in an "insert
       linefeed" mode. That is, whenever the user types carriage



                                                               [page 13]

     NWG/RFC# 726                          JBP DHC 8-MAR-77 08:29  39237
     Remote Controlled Transmission & Echoing Telnet Option



       return <cr> the user Telnet sends both carriage return
       and linefeed <cr><lf> (the Telnet end of line signal).
       When space character occurs at the end of a line in the
       example description it is shown explicitly by <sp> to
       avoid confusion. Other uses of the space character are
       not so marked to avoid destroying the readability of the
       example.                                                       7c

       A Telnet connection has already been opened, but the
       TENEX prompt has not yet been issued. The hosts first
       discuss using the RCTE option:                                 7d

         S: <IAC><WILL><RCTE>                                        7d1

         U: <IAC><DO><RCTE>                                          7d2

         S: TENEX 1.31.18, TENEX EXEC 1.50.2<cr><lf>@
            <IAC><SB><RCTE><11><1><24><IAC><SE>                      7d3

           [Print the herald and echo input text up to a break
           character, but do not echo the break character.
           Classes 4 (Format Effectors), 5 (Non-format Effector
           Controls and <DEL>), and 9 (<sp>) act as break
           characters.]                                             7d3a

         P: TENEX 1.31.18, TENEX EXEC 1.50.2<cr><lf>@                7d4

         T: LOGIN ARPA<cr>                                           7d5

         P: LOGIN                                                    7d6

         U: LOGIN<sp>                                                7d7

         U: ARPA<cr><lf>                                             7d8

         S: <sp><IAC><SB><RCTE><0><IAC>SE>                           7d9

         P: <sp>ARPA                                                7d10

         S: <cr><lf>(PASSWORD): <IAC><SB><RCTE><7><IAC><SE>         7d11

         P: <cr><lf>(PASSWORD):<sp>                                 7d12

         T: WASHINGTON 1000<cr>                                     7d13

           [The password "WASHINGTON" is not echoed. Printing of
           "1000<cr>" is withheld]                                 7d13a

         U: WASHINGTON<sp>                                          7d14



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     NWG/RFC# 726                          JBP DHC 8-MAR-77 08:29  39237
     Remote Controlled Transmission & Echoing Telnet Option



         U: 1000<cr><lf>                                            7d15

         S: <sp><IAC><SB><RCTE><3><IAC><SE>                         7d16

         S: <cr><lf>JOB 17 ON TTY41 7-JUN-73 14:13<cr><lf>@
            <IAC><SB><RCTE><0><IAC><SE>                             7d17

         P: <sp>1000                                                7d18

           [Printing is slow at this point; so the account
           number is not printed as soon as the server's command
           for it is received.]                                    7d18a

         P: <cr><lf>JOB 17 ON TTY41 7-JUN-73 14:13<cr><lf>@         7d19

         T: DED<esc><cr>                                            7d20

         P: DED                                                     7d21

         U: DED<esc>                                                7d22

         S: .SAV;1<IAC><SB><RCTE><0><IAC><SE>                       7d23

         P: .SAV;1                                                  7d24

         U: <cr><lf>                                                7d25

         S: <cr><lf><lf>DED    3/14/73 DRO,KRK<cr><lf>:
            <IAC><SB><RCTE><15><1><IAC><255><IAC><SE>               7d26

           [The program is started and the DED prompt ":" is
           sent. At the command level, DED responds to every
           character. The server sets the break classes to all
           classes.]                                               7d26a

         P: <cr><lf><lf>DED    3/14/73 DRO,KRK<cr><lf>:             7d27

         T: IThis is a test line.<cr>This is another test
            line.<^Z>Q                                              7d28

           ["I" means Insert Text. The text follows, terminated
           by a Control-Z. The "Q" instructs DED to Quit.]         7d28a

         U: I                                                       7d29

         U: This is a test line.<cr><lf>                            7d30

         S: I<cr><lf>*<IAC><SB><RCTE><11><0><24><IAC><SE>           7d31




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     NWG/RFC# 726                          JBP DHC 8-MAR-77 08:29  39237
     Remote Controlled Transmission & Echoing Telnet Option



           [DED prompts the user, during text input, with an
           asterisk at the beginning of every line. The server
           sets the break classes to classes 4 and 5, the format
           effectors and the non-format effector controls.]        7d31a

         P: I<cr><lf>*This is a test line.                          7d32

         S: <cr><lf>*<IAC><SB><RCTE><0><IAC><SE>                    7d33

         P: <cr><lf>*This is another test line.                     7d34

         U: This is another test line.<^Z>                          7d35

         U: Q                                                       7d36

           [Note that the "Q" will not immediately be printed on
           the terminal, since it must wait for authorization.]    7d36a

         S: ^Z<cr><lf>:<IAC><SB><RCTE><15><1><IAC><255><IAC><SE>    7d37

           [The returned "^Z" is two characters, not the ASCII
           Control-Z or <sub>.]                                    7d37a

         S: Q<cr><lf>@<IAC><SB><RCTE><11><1><24><IAC><SE>           7d38

         P: Q<cr><lf>@                                              7d39

         And the user is returned to the Exec level.                7d40
























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