Network on-line operators
RFC - Unknown
(April 1971; No errata)
||RFC Editor Note
RFC 121 (Unknown)
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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
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
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.
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
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