RFC121 - Network on-line operators

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　　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.

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:

(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

(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

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

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

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:

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

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.

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'

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.

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

(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 RFCwas put into machine readable form for entry ]
[ into the online RFCarchives by Gruss Gottfried 01/98 ]

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