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rfc:rfc121

Network Working Group M. Krilanovich Request for Comments: 121 Computer Research Lab, UCSB NIC: 5833 21 April 1971

                     NETWORK ON-LINE OPERATORS

PREFACE

 The operators described in this document have been implemented within
 UCSB's On-Line System and make the Network (via the NCP) accessible
 to On-Line System users.
 A set of operators is provided to facilitate the use of the Network
 by On-Line System users.  The operators are defined on LVL I on
 system 'NET', and serve an an interface between the users and the
 Network Control Program (NCP), which supervises all Network
 operations at this site.
 A concept fundamental to On-Line System Network operations is that of
 a completion code variable.  Associated with each socket that is not
 in the closed state is a unique variable, called a completion code
 variable.  This variable serves two purpose: it identifies the local
 socket referenced, and upon completion of the operation it contains a
 completion code to indicate the outcome of the operation to the user.
 It may be used at any time for any purpose other than Network
 operations.  Its value at the beginning of a Network operation is
 immaterial rather it is the variable itself that is important.  In
 all Network operations, whenever a completion code variable is called
 for, the only acceptable type variable is a LO storage location,
 either case 1 or case 2.
 In those operations requiring a socket to be specified by its socket
 identifier, the following format is used: the site number of UCSB is
 always used for local sockets, and so this item is never specified.
 The site number of a foreign socket, if specified, must be a positive
 integer or a LO storage location, and must be less then 256 in value.
 If not specified, the site number of a foreign socket will default to
 the site number of UCSB.  A socket number is specified as an integer,
 either unsigned, in which case it is assumed to be positive, or with
 an explicit minus sign, or a LO storage location, of any value.
 Negative socket numbers are represented internally in two's
 complement form and therefore for the purpose of the gender of a
 socket, a socket number is even or odd according to whether its
 absolute value is even or odd, respectively.

Krilanovich [Page 1] RFC 121 Network On-Line Operators April 1971

 In all operations involving the On-Line System Network operators,
 there are certain conventions concerning the format of the data sent
 and received.  The data is grouped in 'messages' consisting of three
 fields, op code, length, an text, in that order.  The op code is one
 byte in length and is a code which indicates how the text field is to
 be interpreted.  The length field is two bytes long, and gives the
 length, in bits, of the text field, which contains the actual data.
 (The op code and length fields together are termed a header.)
 The following op codes are presently defined:
   op code                        meaning
     0          This op code is a NOP.  No text field exists, and the
                contents of the length field are unpredictable. (This
                op code is used mainly as a delimiter.)
     1          The text field contains EBCDIC characters, one
                character per byte.  The On-Line System operators
                consider the characters as intended for display as
                soon as the text field has been received.
     2          The text contains codes for keypushes, one byte per
                key.  The On-Line operators consider the keys as
                intended for execution as soon as the text field has
                been received.
     3          The same as for an op code of 2, except that the On-
                Line operators consider that the execution of the keys
                will be delayed until all data for that receive
                operation has been received.
 The standard format of data sent or received by the On-Line System
 operators is a string of messages, with the last message indicated by
 a header with a NOP op code, called a trailer.  These conventions are
 the default situation; any of them may be overridden by appropriate
 programming.  Following is a description of each operator, its
 function and key sequence.
 (1) OPEN
    By invoking this operator, the user requests that the specified
    local socket be removed from the closed state and thus be prepared
    to participate in data transfer.  There are three distinct
    operations that can be performed by this operator and these are
    described below:

Krilanovich [Page 2] RFC 121 Network On-Line Operators April 1971

    (A) CONNECT
       By invoking this operator, the user requests that the specified
       local socket be logically connected to the specified foreign
       socket, and that transfer of data be enabled between the two
       sockets.  Processing at the terminal is suspended until the
       foreign sockets either accepts or rejects the connection
       attempt.  This operation is valid only when the local socket is
       in the closed state.
       The key sequence is as follows:
          UP Q1 Q2,Q3[,Q4] RETURN
       where
          Q1 is the completion code variable to be associated with the
             local socket.
          Q2 is the socket number of the local socket.
          Q3 is the socket number of the foreign socket.
          Q4 is the site number of the foreign socket.
    The following completion codes are possible for this operation:
          0, The operation was successful and the connection has been
             established
          4, The specified completion code variable is already
             assigned to a socket; the operation was suppressed
          8, The specified local socket is not in the closed state;
             the operation was suppressed
          12, All communication paths to the specified foreign site
             are in use; the operator was suppressed
          16, Local resources are insufficient to support another
             connection; the operation was suppressed
          20, The connection attempt was rejected by the foreign
             process
          28, The specified foreign site is invalid; the operation was
             suppressed
          36, Either hardware at the foreign site is inoperative or
             the NCP's counter-part at the foreign site does not exist
             or has failed
          40, Local and foreign sockets are both either send or
             receive sockets; the operation was suppressed
          44, By operator command, all Network operations were
             terminated; the socket will be closed
          60, An NCP control transmission error occurred; the
             operation as suppressed

Krilanovich [Page 3] RFC 121 Network On-Line Operators April 1971

    (B) LISTEN
       This operation is a request for notification of any connection
       attempt directed toward the specified local socket.  Processing
       at the terminal is suspended until such a call is received.
       This operation is valid only when the designated local socket
       is in the closed state.
       The key sequence is as follows:
          UP Q1 Q2 RETURN
       where
          Q1 is the completion code variable to be associated with the
             local socket.
          Q2 is the socket number of the local socket.
          The following completion codes are possible for this
             operation:
          0, The operation was successful and a call has been received
          4, The specified completion code variable is already
                    assigned to a socket; the operation was suppressed
          8, The specified local socket is not in the closed state;
                    the operation was suppressed
          12, Local resource are insufficient to support another
                    connection; the operation was suppressed
          44, By operator command, all Network operations were
                    terminated; the socket will be closed
    (C) ACCEPT
       This operation accepts connection with the foreign socket whose
       call caused successful completion of a previous LISTEN
       operation by the specified local socket.  After completion of
       this operation, data may be transferred to or from the local
       socket, depending on its gender.  This operation is valid only
       when the last operation referencing the local socket as a
       LISTEN operation.  Processing at the terminal is suspended
       until the operation is completed.
    The key sequence is as follows:
          UP Q RETURN

Krilanovich [Page 4] RFC 121 Network On-Line Operators April 1971

    where
          Q is the completion code variable associated with the local
             socket by a previous LISTEN operation.
             The following completion codes are possible for this
             operation:
                0, The operation as successful, and the connection is
                    established
                4, The specified local socket is in the closed state
                    (the NCP may have received an abort notification
                    from the foreign process); the operation was
                    suppressed
                8, The previous operation specifying the designated
                    local socket was not a LISTEN; the operation was
                    suppressed
                12, All communication paths to the specified foreign
                    site are in use; the socket has been returned to
                    the closed state
 (2) CLOSE
    This operation is a request that the specified local socket be
    returned to the closed state.  If the last operation involving
    this socket was a LISTEN, this operation refuses the foreign
    process connection attempt.  If the last operation was a CONNECT,
    the attempt is aborted.  If a connection is established, any data
    in transit form the local socket is allowed to reach the foreign
    socket and to be either received or flushed before the local
    socket is closed.
    Processing at the terminal is suspended until the socket has been
    returned to the closed state.
    The key sequence is as follows:
          DWN Q

Krilanovich [Page 5] RFC 121 Network On-Line Operators April 1971

    where
          Q  is the completion code variable associated with the local
             socket.
          The following completion codes are possible for this
          operation:
                0, The operation was successful, and the socket has
                    been returned to the closed state
                8, The specified completion code variable is not
                    currently assigned to a socket; the operation was
                    suppressed
                12, The specified local socket is in the process of
                    being closed the operation was suppressed, but the
                    local socket will be closed
                36, Either hardware at the foreign site is
                    inoperative, or the NCP's counterpart at the
                    foreign site does not exist or has failed
                44, By operator command, all Network operations were
                    terminated; the socket will be closed
                60, An NCP control transmission error occurred; the
                    operation was aborted
                64, A transmission error occurred the operation was
                    aborted, but the socket will be closed
 (3) SEND
    This operation caused data to be sent to the foreign socket.
    Processing at the terminal is suspended until the data has been
    received by the foreign socket, or until it has been queued
    locally by the NCP.
    The possible key sequence are as follows:
          STORE  Q1 Q2 text Q2
          STORE +Q1 Q2 text Q2
          STORE -Q1 Q2 text Q2
          STORE .Q1[X]Q3 RETURN
    where
          Q1 is the completion code variable associated with the local
             socket.
          Q2 is any key except RESET.
          'Text' is a string of any length of any keys except Q2 and
             RESET.
          Q3 is an unsigned integer.  If it is preceded by 'X', the

Krilanovich [Page 6] RFC 121 Network On-Line Operators April 1971

             integer is assumed to be in hexadecimal.
             [X]Q3 should have a value less then 256.
    If Q1 is the first key after STORE, the keys comprising 'text' are
    not executed but rather are sent as a one byte code per key, in
    one or more standard messages.  They are preceded by a header with
    the op code which indicates keys to be executed as soon as they
    are received, and followed by a trailer.  If a '+' precedes Q1,
    the headers and the text will be sent, but no trailer.  If a  '-'
    precedes Q1, only the text will be sent.  If a '.' precedes Q1,
    [X]Q3 will be sent as a one byte number, with no header or
    trailer.
    The following completion codes are possible for this operation:
          0, The operation was successful, and the data has been sent
          4, The specified local socket is not a send socket; the
             operation was suppressed
          8, The specified completion code variable is not assigned to
             a socket; the operation was suppressed
          12, A previous send operation is in progress ;the operation
             was suppressed
          16, The connection is not fully open; the operation was
             suppressed
          20, The foreign socket terminated the connection before
             completion of the send operation; not all the data was
             transmitted
          36, Either hardware at the foreign site is inoperative, or
             the NCP's counterpart at the foreign site does not exist
             or has failed
          44, By operator command, all Network operations were
             terminated the socket will be closed
          52, One or more interrupts were received from the foreign
             socket; the operation was suppressed
          60, An NCP control transmission error occurred; the
             operation was aborted and the socket will be closed
          64, A transmission error occurred; the operation was aborted
             and the socket will be closed
 (4) RECEIVE
    This operation causes data to be received from the foreign socket.
    Processing at the terminal is suspended until the data sent by the
    foreign socket has been received by the local socket and
    processed.
    The possible key sequences are as follows:

Krilanovich [Page 7] RFC 121 Network On-Line Operators April 1971

          LOAD  Q1
          LOAD +Q1
          LOAD -Q1 Q2, Q3 RETURN
          LOAD .Q1 Q4 RETURN
    where
          Q1 is the completion code variable associated with the local
             socket.
          Q2 is a positive integer, or a LO storage location, less
             then 256.
          Q3 is a positive integer, or a LO storage location, less
             than 65536
          Q4 is a positive integer less than 5.
    If Q1 is the first key after LOAD, one or more standard messages
    will be received and executed.  The data may or may not be
    executed, as soon as it is received, depending on the op code.
    Processing of manual keypushes is suspended until a trailer is
    received.  If Q1 is preceded by a '+', the operation is as above,
    except that only one message, with no trailer, is received, and
    the operation is only performed if there is data queued for the
    local socket, ready to be received. ('LOAD +' is intended mainly
    for use with the Network On-Line Interface.)  If Q1 is preceded by
    a '-', a string of text whose length, in bits, is Q3, is received
    and processed according to the op code Q2.  If a '.' precedes Q1,
    Q4 bytes of data are read and placed, right justified, in the LO
    accumulator.
    The following completion codes are possible for this operation:
          0, The operation was successful and the data has been
             received
          4, The specified local socket is not a receive socket; the
             operation was suppressed
          8, The specified completion code variable is not assigned to
             a socket; the operation was suppressed
          12, A previous receive operation is in progres; the
             operation was suppressed
          16, The connection is not fully open; the operation was
             suppressed
          20, The foreign socket terminated the connection before
             completion of the receive operation; data is
             unpredictable
          36, Either hardware at the foreign site is inoperative, or
             the NCP's counterpart at the foreign site does not exist
             or has failed
          44, By operator command, all Network operations were

Krilanovich [Page 8] RFC 121 Network On-Line Operators April 1971

             terminated; the socket will be closed
          52, One or more interrupts were received from the foreign
             socket; the operation was suppressed
          60, An NCP control transmission error occurred; the
             operation was suppressed and the socket will be closed
          200, There was no data queued for the local socket; the
             operation was suppressed (applicable only to 'LOAD +')
 (5) CHECK
    This operation causes the status of the specified local socket to
    be displayed.  There is no completion code variable associated
    with this operation, since it is always successful and the socket
    is identified by its socket number.  This operation is valid at
    any time, and with one exception, noted below, is always completed
    immediately.
    The possible key sequences are as follows:
          DISPLAY (Q RETURN...)...
          DISPLAY (Q?)...
          DISPLAY RETURN...
    where
          Q is the socket number of the local socket whose status is
          to be displayed.
    Successive RETURN'S will display the status of local sockets with
    successively higher socket numbers, and once DISPLAY has been
    pushed, it need not be pushed for subsequent occurrences of Q.
    If Q is followed by a '?', processing at the terminal will be
    suspended until the socket is not in the closed state, at which
    time the status will be displayed.  If the socket is not closed at
    the time the '?' is pushed, response is as if the '?' were a
    RETURN.
    If DISPLAY is followed immediately by a RETURN, the status of all
    non-closed sockets owned by the terminal is displayed, each
    preceded by its associated completion code variable.  If this
    information is more than will fit on one tube, successive RETURN'S
    will display the remainder of the information.

Krilanovich [Page 9] RFC 121 Network On-Line Operators April 1971

    The status has the following format:
          'lclno' 'mnem' 'fgnsite' 'fgnno' 'deficit'
    where
          'lclno' is the socket number of the local socket.
          'mnem' is a mnemonic of up to eight characters for the
             status.
          'fgnsite' is the site number of the foreign socket, or
             blank.
          'fgnno' is the socket number of the foreign socket, or
             blank.
          'deficit' is the send/receive deficit in the form
             'bytes.bits', or blank.
    Following are the possible mnemonics, together with their
    interpretations:
       'MNEM'                               MEANING
       ______                               _______
       OPEN           A connection is fully established.
                      No SEND/RECEIVE operation is in progress.
                      'fgnsite' and 'fgnno' are the site number and
                      the socket number of the connected socket.
                      'deficit' is the number of bits queued locally
                      at the socket by the NCP and available to
                      satisfy a future RECEIVE operation, or awaiting
                      output as the result of a previous SEND
                      operation.
       LISTEN         A LISTEN has been issued.
       CONNECT        A CONNECT has been issued. 'fngsite' and 'fgnno'
                      are the site and socket numbers of the foreign
                      socket.
       DECISION       A LISTEN has been completed. 'fgnsite' and
                      'fgnno' are the site and socket numbers of the
                      calling socket.
       CALL(S)        One or more calls have been received for the
                      local socket.  No LISTEN or CONNECT has been
                      issued.
       I/O            A connection is fully established.  A
                      SEND/RECEIVE operation is in progress. 'fgnsite'

Krilanovich [Page 10] RFC 121 Network On-Line Operators April 1971

                      and 'fgnno' are the site and socket numbers of
                      the connected socket. 'deficit' is the number of
                      bits yet to be sent or received.
       CLOSED         The socket is in the closed state.
       <--DRAIN       The foreign socket is attempting to close the
                      connection.  The NCP has data yet to be read by
                      the local socket. 'fgnsite' and 'fgnno' are the
                      site and socket numbers of the connected socket.
                      'deficit' is the number of bits yet to be
                      received.
       DRAINED        The foreign socket is attempting to close the
                      connection.  The NCP is awaiting arrival at the
                      foreign site of data currently in transit.
                      'fgnsite' and 'fgnno' are the site and socket
                      numbers of the connected socket.
       CLOSING        The local socket has issued a CLOSE.  The NCP is
                      in the process of returning  the local socket to
                      the closed state. 'fgnsite' and 'fgnno' are the
                      site and socket numbers of the connected socket.
       DRAIN-->       The local socket has issued a CLOSE.  The NCP is
                      completing the last SEND operation before
                      returning the local socket to the closed state.
                      'fgnsite' and 'fgnno' are the site and socket
                      numbers of the connected socket. 'deficit' is
                      the number of bits the NCP has yet to transmit.
 (6) IDENTIFY
    This operation is used to identify a local socket by its
    completion code variable.  The operation is valid at any time, and
    is always completed immediately.  Since it is always successful,
    there are no completion codes for the operation, and the contents
    of the completion code variable are not changed.
    The key sequence is:
          ID Q...
    where
          Q is the completion code variable associated with the local
             socket.

Krilanovich [Page 11] RFC 121 Network On-Line Operators April 1971

    The response is a display of Q, followed by 'IS UNDEFINED' if the
    socket is in the closed state, or the socket number associated
    with it if it is not closed.  After ID has been pushed once, it
    need not be pushed again for subsequent occurrences of Q.
 (7) PURGE
    This operator is used to dissociate all completion code variables
    from sockets, and to issue a CLOSE to all sockets currently in use
    at the terminal.  The operation is valid at any time, and is
    always completed immediately.  Since it is always successful.
    there are no completion codes for the operation, and the contents
    of the completion code variables are not changed.
    The key sequence is:
          DEL RETURN
 (8) SIGNAL
    This operation is used to convey a signal to the foreign process.
    The significance of the signal is completely user-dependent.  The
    effect is that the next time the foreign socket attempts to
    initiate a RECEIVE or SEND operation, the operation will be
    suppressed, and a completion code supplied indicating that a
    signal had been received.  Processing at the terminal is suspended
    until the signal has been sent to the foreign NCP.  This operation
    is valid only when the socket is fully open.
    The key sequence is:
          REFL Q
    where
          Q is the completion code variable associated with the local
             socket.
    The following completion codes are possible for this operation:
          0, The operation was successful, and the signal has been
             sent
          4, The specified completion code variable is not assigned to
             a socket; the operation was suppressed
          8, The connection is not fully open;the operation was
             suppressed

Krilanovich [Page 12] RFC 121 Network On-Line Operators April 1971

    (9) CONVERSATIONAL CONTROLLER
    This operator is intended primarily for use with the Network On-
    Line Interface, and is used to carry on a 'conversation' with the
    foreign process.  Any data queued locally for the specified local
    receive socket is received and displayed as characters.  Any keys
    pushed will be sent from the specified local send socket.  The
    user has the option of specifying whether or not upper keyboard
    buttons are to be sent.  In any case, the buttons ERASE, REPEAT,
    ENTER, PRED, and RESET, will not be sent, and pushing any of
    these, except RESET, will cause suspension of data reception until
    a button other than these four is pushed.  Pushing RESET always
    terminates the operation.
    The key sequence is as follows:
          ARG [,] [-]Q1[-]Q2
    where
          Q1 is the completion code variable associated with the local
             send socket.
          Q2 is the completion code variable associated with the local
             receive socket.
    If ARG is followed by ',', both upper and lower keyboard buttons
    will be sent, and the operation will be terminated only by pushing
    RESET.  If no ',' follows ARG, only lower keyboard buttons will be
    sent, and the operation is terminated by pushing RESET or any
    upper keyboard button.  If a '-' precedes Q1, no headers will be
    sent, and if a '-' precedes Q2, no headers will be received.  In
    any case, if headers are to be received, the operation is
    terminated when a trailer is received, and a corresponding trailer
    is sent if headers are to be sent.
    The completion codes for the send socket are the same as for the
    SEND operation, and the completion codes for the receive socket
    are the same as for the RECEIVE operation.  If a non-zero
    completion code is found, a message is displayed, either 'OUTPUT
    ERROR' or 'INPUT ERROR', depending on whether the send socket for
    the receive socket encountered the non-zero completion code, and
    the operation is terminated.
        [ This RFC was put into machine readable form for entry ]
        [ into the online RFC archives by Gruss Gottfried 01/98 ]

Krilanovich [Page 13]

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