rfc466.txt

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Network Working Group                                          J. Winett
Request for Comments: 466                                          LL-67
NIC: 14740                                              27 February 1973
Category: TELNET


                  TELNET LOGGER/SERVER For Host LL-67

   The attached writeup documents the TELNET LOGGER/SERVER for the
   CP/CMS system on the Lincoln Laboratory 360>67 (host 10).  The
   facility serves both half duplex and full duplex TELNET users with
   data in either ASCII or EBCDIC codes.

   Use of the hide-your-input and noecho TELNET controls are used for
   the EBCDIC print suppress (bypass) and print restore features during
   the login procedure.  To support half duplex terminals, the TELNET
   control break (reverse break) is sent as an input prompt when input
   is desired.  This code can also be used to indicate that a previous
   line sent without an end of line sequence (CR-LF) should be printed.
























   This material has not been reviewed for public release and is
   intended only for use with the ARPA network.  It should not be quoted
   or cited in any publication not related to the ARPA network.





Winett                                                          [Page 1]

RFC 466           TELNET LOGGER/SERVER For Host LL-67      February 1973


                    Operation of the Lincoln Laboratory
                        CP/CMS TELNET LOGGER/SERVER

ICP Connection

   The TELNET LOGGER/SERVER follows the ICP protocol for making a pair
   of connections.  The LOGGER is initially enabled for a connection on
   socket X'00000001'.  When an RFC is received for this socket a pair
   of sockets will be chosen for the TELNET connections.  If the maximum
   number of TELNET users which can be served are active, the initial
   connection is refused.  Currently, three TELNET users can be served.

TELNET LOGGER

   After the ICP connections have been setup, the LOGGER expects a
   TELNET data type code, a string of network ASCII characters, or a
   null line (just CR-LF) to indicate whether its operation should be in
   ASCII or in EBCDIC character codes.  ASCII is assumed unless the
   first byte received is the TELNET EBCDIC data type code (X'A2).  When
   something has been received, the message:

                     Lincoln Laboratory CP/CMS Online

   will be transmitted by the LOGGER.  For example, if ASCII operation
   is desired a null line (just CR-LF) transmitted on the send socket
   will cause the welcoming message to be sent in ASCII.  The CP login
   procedure can then begin.  If communications is desired to be carried
   on with EBCDIC character codes, the first byte transmitted should be
   the TELNET data type code for EBCDIC (X'A2').  Thereafter all
   communications will be in the code originally used.

   The CP login procedure expects the user to enter:

                               LOGIN userid

   where the userid specifies the desired virtual machine.  CP then
   replies with:

                              ENTER PASSWORD:

   followed by the EBCDIC code for bypass (x'24') which is mapped into
   the TELNET code hide-your-input.

   The user should then enter a password.  Passwords entered from the
   network may be different from those entered from a local terminal.
   The LOGGER maps network passwords into a corresponding CP password.
   Thus, access to an account can only be made from the network if a
   network password, together with a CP password and userid, is entered



Winett                                                          [Page 2]

RFC 466           TELNET LOGGER/SERVER For Host LL-67      February 1973


   into a file which is read by the LOGGER.  If a userid entered from
   the network is not in the LOGGER FILE (or if the network password
   does not match the one included in the file for the specified userid)
   the LOGGER passes an invalid userid (or password) to CP.  The CP
   response for an invalid userid or password is then sent to the
   network user.

   After a password is received by CP, CP transmits the EBCDIC code for
   restore (X'14') which is mapped into the TELNET control noecho.

TELNET SERVER

   Since the CP/CMS system operates with EBCDIC codes, ASCII codes must
   be translated into EBCDIC before being sent to a virtual machine.
   Figure 1 gives the ASCII codes and their EBCDIC mapping.  When the
   ASCII sequence CR-LF is received, it is mapped into the EBCDIC code
   NL.  Whenever the TELNET control NOP is included in an input string,
   it is mapped into an EBCDIC idle (X'17') and then removed from the
   string.  Thus, if TELNET NOP codes are included between a CR and LF,
   they are removed before the CR-LF is mapped into the EBCDIC NL.

   The TELNET control hide-your-input is mapped into the EBCDIC code for
   bypass (X'24') and the TELNET control echo is mapped into the EBCDIC
   control for restore (X'14').  If the TELNET control echo is received,
   the SERVER should send the control noecho but this feature has not
   yet been implemented.  Instead, the TELNET control echo is mapped
   into the EBCDIC code X'23'.  If the TELNET break is received, it is
   interpreted as an attention signal and the appropriate action is
   taken by CP or CMS.

   CP/CMS is a line at a time system and expects all input to consist of
   lines ending with a NL code.  Characters received are buffered until
   the newline code is received.

   Since CP/CMS is also a half duplex system, characters are only
   examined when the system is expecting input.  If the system is not
   expecting input, a network interrupt is required to cause the SERVER
   to process received characters.  On receipt of a network interrupt,
   characters received before the TELNET data mark is received are
   examined and discarded, except that if a TELNET break code is found,
   the appropriate CP/CMS interrupt action is stimulated.

   On output, EBCDIC codes are mapped into network ASCII if a mapping
   exists; otherwise, the codes are mapped into the TELNET control NOP.
   A NL code is mapped into CR-LF.  The EBCDIC code for bypass maps into
   the TELNET control hide-your-input and the EBCDIC code for restore
   maps into the TELNET control noecho.  Also, the code X'23' maps into
   the TELNET control echo and the code X'38' maps into the TELNET



Winett                                                          [Page 3]

RFC 466           TELNET LOGGER/SERVER For Host LL-67      February 1973


   control break.

   Since CP/CMS is a line at a time, half duplex system the TELNET
   control break is transmitted as an end of message signal and also as
   an input prompt code.  If characters were output without a NL, the
   break, as an end of message code, indicates to the user TELNET
   operating on a line at a time mode that the characters previously
   transmitted should be printed without waiting for the end of line
   sequence.  If the user TELNET is also operating in a half duplex
   mode, the break as an input prompt indicates that the system is ready
   for input.

   If input had been anticipated and sent by a full duplex user TELNET,
   the TELNET SERVER will have that input available for immediate
   processing.  Thus, in the case of a full duplex user TELNET the break
   as a prompt should be ignored.

   Though CP/CMS operates in a half duplex mode, it supports half duplex
   terminals with the reverse break feature allowing the system to abort
   an input mode in order to transmit a priority output message.  In
   this situation, the TELNET SERVER transmits a TELNET SYNC.  A half
   duplex user TELNET should interpret this by aborting the input mode,
   i.e., revoking a previous TELNET break which was interpreted as an
   input prompt.

   No codes in the output character stream can cause the TELNET data
   mark to be transmitted.

LOGOUT

   When a user logs out from his virtual machine, CP passes the
   equivalent of a line disconnect to the LOGGER.  The LOGGER then
   closes the TELNET send and receive sockets.


















Winett                                                          [Page 4]

RFC 466           TELNET LOGGER/SERVER For Host LL-67      February 1973


   ASCII    ASCII    ASCII    SYMBOLS    EBCDIC    EBCDIC
   DEC      OCT      HEX                 HEX       DEC

     0        0      (00)      NUL       (00)       00
     1        1      (01)      SOH       (01)       01
     2        2      (02)      STX       (02)       02
     3        3      (03)      ETX       (03)       03
     4        4      (04)      EOT       (37)       55
     5        5      (05)      ENQ       (2D)       45
     6        6      (06)      ACK       (2E)       46
     7        7      (07)      BEL       (2F)       47
     8       10      (08)      BS        (16)       22
     9       11      (09)      HT        (05)       05
    10       12      (0A)      LF        (25)       37
    11       13      (0B)      VT        (0B)       11
    12       14      (0C)      FF        (0C)       12
    13       15      (0D)      CR        (0D)       13
    14       16      (0E)      SO        (0E)       14
    15       17      (0F)      SI        (0F)       15
    16       20      (10)      DLE       (10)       16
    17       21      (11)      DC1       (11)       17
    18       22      (12)      DC2       (12)       18
    19       23      (13)      DC3       (13)       19
    20       24      (14)      DC4       (3C)       60