RFC120 - Network PL1 subprograms

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　　NETWORK PL1 SUBPROGRAMS

April 21, 1971

Mark Krilanovich

Computer Research Lab

University of California

Santa Barbara, California

PREFACE

The subroutines described in this document have been implemented at UCSB
and make the Network (via the NCP) accessible to PL1 programs executing
in the 360/75. They are callable from within any PL1 main program or
subroutine compiled at UCSB.

A set of assembly-language written subprograms is provided to
facilitate the use of the Network by PL1 programmers. They serve as
an interface between the user and the Network Control Program (NCP),
which supervises all Network operations at this site.

A concept fundamental to PL1 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 purposes: 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 programmer. 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 attributes for the
variable are BINARY FIXED(31,0)ALIGNED.

In general, the subprograms will initiate the operation, and enter
the WAIT state (consume no CPU time) until notified by the NCP of the
completion of the operation. For such operations, the programmer
supplies a time limit, with attributes BINARY FIXED(31,0), which
specifies, in tenths of a second, the maximum length of time the
subprogram is to wait for the operation to complete. If this time
limit is exceeded, a completion code is supplied to indicate the
error, and control is returned to the calling program, with the
operation still pending.

In those operations requiring a socket to be specified by its socket
identifier, the following format is used. The identifier is
specified as a BINARY FIXED(31,0) array, singly dimensioned with at
least two elements, and with a lower subscript bound of one. The
first element is taken to be the site number, and the second element
the socket number. A socket number may have any value, positive,
negative, or zero. Since negative numbers are represented internally
in two's complement form, for the purposes of the gender of a socket,
a socket number is even or odd according to whether its absolute
value is even or odd, respectively.

Following is a description of each subprogram, its function and
calling sequence.

(1) OPEN

By invoking this subprogram, 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 subprogram, and these are
described below:

(A) CONNECT

By initiating this operation, the user requests that the
specified local socket be logically connected to the specified
foreign socket, and that data transfer between the two sockets
be enabled. The subprogram will wait until the foreign socket
either accepts or rejects the connection attempt. This
operation is valid only when the socket is in the closed
state.

The calling sequence is as follows:

CALL @OPEN(cmpcd, time,lclsck,fgnsck,ws);

where

'cmpcd' is the completion code variable to be associated
with the local socket.
'time' is the length of time the subprogram is to wait
for the completion of the operation.
'lclsck' is the socket identifier of the local socket.
'fgnsck' is the socket identifier of the foreign socket.
'ws' is a workspace which has the same attributes as a
socket identifier, and, if the operation if
successful, will become associated with the local
socket for the life of the connection. In response
to certain future operations, information may be
returned to the programmer in this workspace.

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 operation 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
24, The specified local socket is not local to UCSB; the
operation was suppressed
28, The specified foreign site is invalid; the operation
was suppressed
32, An addressing or protection exception was encountered
with respect to the specified workspace; the
operation was suppressed
36, Either hardware at the foreign site is inoperative or
the NCP's counterpart 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 occured; the
operation was suppressed
252, The specified time limit was exceeded; the operation
was initiated but not completed

(B) LISTEN

This operation is a request for notification of any connection
attempt directed toward the specified local socket. The
subprogram waits until such a call is received, at which time
the calling process' socket identifier is returned to the
calling program. This operation is valid only when the
designated local socket is in the closed state. The calling
sequence is as follows:

CALL @OPEN(cmpcd, time,lclsck,ws);

where

'cmpcd' is the completion code variable to be associated
with the local socket.
'time' is the length of time the subprogram is to wait
for the completion of the operation.
'lclsck' is the socket identifier of the local socket.
'ws' is a workspace which, if the operation is
successful, will contain the socket identifier of
the calling socket, and will become associated with

the local socket for the life of the connection.
'ws' has the same attributes as a socket identifier.

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 resources are insufficient to support another
connection; the operation was suppressed
16, The specified local socket is not local to UCSB; the
operation was suppressed
20, An addressing or protection exception was encountered
with respect to the specified workspace; the
operation was suppressed
44, By operator command, all Network operations were
terminated; the socket will be closed
252, The specified time limit was exceeded; the operation
was initiated but not completed

(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 was a
LISTEN operation. The subprogram will wait until the
operation is completed.

The calling sequence is as follows:

CALL @OPEN(cmpcd, time);

where

'cmpcd' is the completion code variable associated with
the local socket by a previous LISTEN operation.
'time' is the length of time the subprogram is to wait
for the completion of the operation.

The following completion codes are possible for this
operation:

0, The operation was 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
252, The specified time limit was exceeded; the operation
was initiated but not completed

(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 from the local socket is allowed to reach the foreign
socket and to be either received or flushed before the local socket
is closed. The subprogram will wait until the socket has been
returned to the closed state.

The calling sequence is as follows:

CALL @CLOSE(cmpcd,time);

where

'cmpcd' is the completion code variable associated with the
local socket.
'time' is the length of time the subprogram is to wait for the
completion of the operation.

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 occured; the operation
was aborted
64, A transmission error occured; the operation was aborted,
but the socket will be closed
252, The specified time limit was exceeded; the operation was
initiated but not completed

(3) SEND

This operation causes data to be sent to the foreign socket. The
subprogram will wait until the data has been received by the
foreign socket, or until it has been queued locally by the NCP.

The calling sequence is as follows:

CALL @WRITE(cmpcd, bfr,len,time[,offset]);

where

'cmpcd' is the completion code variable associated with the
local socket.
'bfr' is the data to be sent, and must be a singly dimensioned
array, either DECIMAL or BINARY, FIXED or FLOAT.
'len' is the number of bits of data to be sent. If 'len' is
non-positive, no operation is performed. 'len' has the
attribute BINARY FIXED(31,0).
'time' is the length of time the subprogram is to wait for the
completion of the operation.
'offset' is the bit offset from the first bit of 'bfr' at
which data transmission is to begin, and must have the
attributes BINARY FIXED(31,0). If not specified,
'offset' defaults to zero.

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 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
56, An addressing exception was encountered with respect to
the data buffer; the operation was suppressed
60, An NCP control transmission error occured; the operation
was suppressed
64, A transmission error occured; the operation was aborted,
and the socket will be closed
252, The specified time limit was exceeded; the operation was
initiated but not completed

(4) RECEIVE

This operation causes data to be received from the foreign socket.
The subprogram will wait until the reception of data is complete.

The calling sequence is as follows:

CALL @READ(cmpcd,bfr,len,time[,offset]);

where

'cmpcd' is the completion code variable associated with the
local socket.
'bfr' is the variable into which the data is to be placed, and
must be a singly dimensioned array, DECIMAL or BINARY,
FIXED or FLOAT.
'len' is the number of bits of data to be received. If 'len'
is non-positive, no operation is performed. 'len' has
the attribute BINARY FIXED(31,0).
'time' is the length of time the subprogram is to wait for the
completion of the operation.
'offset' is the bit offset from the first bit of 'bfr' at
which the first bit of data is to be placed, and must
have the attributes BINARY FIXED(31,0). If not
specified, 'offset' defaults to zero.

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 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 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
24, An addressing or protection exception was encountered with
respect to the data buffer; the operation was suppressed
52, One or more interrupts were received from the foreign
socket; the operation was suppressed
60, An NCP control transmission error occured; the operation
was aborted, and the socket will be closed
252, The specified time limit was exceeded; the operation was
initiated but not completed

(5) CHECK

This operation causes the status of the specified local socket to
be returned. 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 is always completed immediately.

The calling sequence is as follows:

CALL @CHECK(lclsck,stat,mnem,fgnsck,deficit);

where

'lclsck' is the socket identifier of the local socket.
'stat' is a code for the status, and has the attribute BINARY
FIXED(31,0).
'mnem' is a mnemonic for the status, and has the attribute
CHARACTER, of any fixed length greater than or equal to
eight. If 'mnem' is longer than eight bytes, it will be
padded to the right with blanks.
'fgnsck' is the socket identifier of the foreign socket, or
zero.

'deficit' is the send/receive deficit in bits, or zero, and
has the attributes BINARY FIXED(31,0).

'lclsck' is the only argument the programmer need define;
the others are output from the subprogram.

Following are the possible status codes, together with their
mnemonics and interpretations.

'STAT' 'MNEM' MEANING
---- ----
0 OPEN A connection is fully established. No
SEND/RECEIVE operation is in progress.
'fgnsck' is the socket identifier 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.

1 LISTEN A LISTEN has been issued.

2 CONNECT A CONNECT has been issued. 'fgnsck' is the
socket identifier of the foreign socket.

3 DECISION A LISTEN has been completed. 'fgnsck' is
the socket identifier of the calling
socket.

4 CALL(S) One or more calls have been received for
the local socket. No LISTEN or CONNECT has
been issued.

5 I/O A connection is fully established. A
SEND/RECEIVE operation is in progress.
'fgnsck' is the socket identifier of the
connected socket. 'deficit' is the number
of bits yet to be sent or received.

6 CLOSED The socket is in the closed state.

7 <--DRAIN The foreign socket is attempting to close
the connection. The NCP has data yet to be
read by the local socket. 'fgnsck' is the
socket identifier of the connected socket.
'deficit' is the number of bits yet to be
received.

8 DRAINED The foreign socket is attempting to close
the connection. The NCP is awaiting
arrival at the foreign site of data
currently in transit. 'fgnsck' is the
socket identifier of the connected socket.

9 CLOSING The local socket has issued a CLOSE. The
NCP is in the process of returning the
local socket to the closed state. 'fgnsck'
is the socket identifier of the connected
socket.

10 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. 'fgnsck' is the socket
identifier 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 calling sequence is as follows:

CALL @ID(cmpcd,lclsck);

where

'cmpcd' is the completion code variable to be associated with
the local socket
'lclsck' is set to the socket identifier of the local socket
if the completion code variable is associated with a
socket, or to zero otherwise.

(7) 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. The subprogram will wait until the signal has

been sent to the foreign NCP. This operation is valid only when
the socket is fully open.

The calling sequence is as follows:

CALL @ID(cmpcd,time);

where

'cmpcd' is the completion code variable associated with the
local socket.
'time' is the length of time the subprogram is to wait for
completion of the operation.

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

Certain of the Network subprograms are intended for, although not
restricted to, use with the On-Line System Network operators. The
following is a general description of these operators:

In all Network 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, and 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 The 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 Network 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 text 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 are descriptions of those subprograms intended for use with
the On-Line System operators.

(8) WRITE TO ON-LINE CONSOLE

This subprogram causes data, assumed to be characters represented
by their EBCDIC codes, to be sent from the specified local socket.
The characters are sent in a standard message, preceded by a
header, and optionally followed by a trailer. The subprogram waits
for the data to be received by the foreign socket, or to be queued
locally by the NCP. This operation is valid only when the local
socket is a send socket, and is fully open.

The calling sequence is as follows:

CALL @WTOLC(cmpcd,bfr,len,level,across,down,time);

where

'cmpcd' is the completion code variable associated with the
local socket.
'bfr' is the character string to be sent, and must have the
attribute STRING, either CHARACTER or BIT, of any length,
fixed or varying.
'len', in absolute value, is the number of characters to be
sent. If 'len' is positive or zero, the end of the data
is indicated by a trailer; if 'len' is negative, no
trailer is sent. 'len' has the attributes BINARY
FIXED(31,0).
'level' indicates the mode of typing. The absolute value of
'level', if non-zero, is the shift level on which to
type, and must be less than or equal to nine. If greater
than nine, one is used. If 'level' is positive, 'across'

and down are relative to the current typing location. If
'level' is negative, the carriage is positioned to the
upper left-hand corner before typing begins, thus making
'across' and 'down' absolute coordinates. If 'level' is
zero, the typing is in case one characters, and a
carriage return precedes the positioning for 'across' and
'down'. If the characters to be displayed are case one
characters, the header sent will have an op code which
indicates characters to be displayed as soon as they are
received; otherwise, the op code will indicate buttons
to be executed as soon as received. 'level' has the
attributes BINARY FIXED(31,0).
'across' is the number of spaces to be moved horizontally
across the display tube before beginning to type.
'across' can have any value, positive, negative, or zero,
and has the attributes BINARY FIXED(31,0).
'down' is the number of lines to be moved vertically down the
display tube before beginning to type. 'down' can have
any value, positive, negative, or zero, and has the
attributes BINARY FIXED(31,0).
'time' is the length of time the subprogram is to wait for the
completion of the operation.

The completion codes for this operation are the same as for SEND.

(9) READ FROM ON-LINE CONSOLE

This subprogram receives data, assumed to be characters represented
by their EBCDIC codes, from the foreign socket in one or more
standard messages. The subprogram will wait for the data,
optionally followed by a trailer, to be received by the local
socket. This operation is valid only when the local socket is a
receive socket and is fully open.

The calling sequence is as follows:

CALL @RFOLC(cmpcd,bfr,len,time);

where

'cmpcd' is the completion code variable associated with the
local socket.
'bfr' is the variable into which the data is to be placed, and
has the attribute CHARACTER, of any fixed length. If the
length of 'bfr' is greater than the amount of data
received, 'bfr' will be padded to the right with blanks.
'len', in absolute value, is the maximum number of characters
to be placed in 'bfr'. If the length fields of the

header(s) received total more data than 'len', the excess
data will be received, but will not be placed into 'bfr',
and will not be accessible to the program. If 'len' is
positive or zero, data will be received until a trailer
is encountered. If 'len' is negative, a single message,
exclusive of trailer, will be received. 'len' has the
attributes BINARY FIXED(31,0).
'time' is the length of time the subprogram is to wait for the
completion of the operation.

The completion codes for this operation are the same as for
RECEIVE.

(10) WRITE TO ON-LINE CONSOLE WITH REPLY

This subprogram combines the functions of 'WRITE TO ON-LINE
CONSOLE' and 'READ FROM ON-LINE CONSOLE'. The subprogram first
sends a string of data to the foreign socket from the specified
send socket, waits for it to be received by the foreign socket (or
queued locally by the NCP), and then waits for a reply directed
toward the specified receive socket. The operation is valid only
when the sockets have the correct gender and both are fully open.

The calling sequence is as follows:

CALL @WTOLCR(cmpcd, bfr, len, level, across, down, time,
cmpcd2, bfr2, len2);

where

'cmpcd' is the completion code variable associated with the
local send socket.
'bfr' is as in 'WRITE TO ON-LINE CONSOLE'.
'len' is as in 'WRITE TO ON-LINE CONSOLE'.
'level' is as in 'WRITE TO ON-LINE CONSOLE'.
'across' is as in 'WRITE TO ON-LINE CONSOLE'.
'down' is as in 'WRITE TO ON-LINE CONSOLE'.
'time' is the length of time the subprogram is to wait for
completion, individually, of the transmission and
reception of data.
'cmpcd2' is the completion code variable associated with the
local receive socket.
'bfr2' is as 'bfr' in 'READ FROM ON-LINE CONSOLE'.
'len2' is as 'len' in 'READ FROM ON-LINE CONSOLE'.

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.

(11) ERASE

This subprogram causes data constituting an On-Line System command
to erase the display tube to be sent from the specified local
socket. The data is sent in a single standard message, including
an op code indicating characters to be displayed as they are
received, and optionally including a trailer. The subprogram
waits for the data to be received by the foreign socket, or to be
queued locally by the NCP. This operation is valid only when the
local socket is a send socket, and is fully open.

The calling sequence is as follows:

CALL @ERASE(cmpcd,delay1,delay2,time);

where

'cmpcd' is the completion code variable associated with the
local socket.
'delay1', in absolute value, is the length of time, in tenths
of a second, the subprogram is to pause (in the WAIT
state) before sending the erase. If 'delay1' is
positive or zero, a trailer will be sent after the
erase; if negative, no trailer will be sent. 'delay1'
has the attributes BINARY FIXED(31,0).
'delay2', is the length of time, in tenths of a second, the
subprogram is to pause after sending the erase and
before returning control to the calling program, and has
the attributes BINARY FIXED(31,0).
'time' is the length of time the subprogram is to wait for
the completion of the operation.

The completion codes for this operation are the same as for SEND.

[ This RFCwas put into machine readable form for entry ]
[ into the online RFCarchives by Rune Skaarsmoen 6/97 ]

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