RFC 121: Network on-line operators

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.






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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:





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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




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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






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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












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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



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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:




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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



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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.








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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'



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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.




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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





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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 ]





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RFC 121: Network on-line operators