Campbell LoggerNet, Инструкция по эксплуатации, Страница: 447 / 580

Section 11. Utilities Installed with LoggerNet Admin and LoggerNet Remote
well being of that record. The server moves on to
the next record.
Stop Note that in the Session Open and Server
Registered states there are “exit” actions that
need to be executed on the Stop event.
Communications between the client and server are conducted using ASCII
records where each record is terminated by a carriage return – line feed (CRLF)
pair. Record length varies quite a bit. For each datalogger record there is
exactly one ASCII record. Because of the Block Mode Protocol used to
communicate with dataloggers, the maximum size datalogger record is limited
to something less than 1024 field values. Assuming 6 characters per value, 13
characters per field name, and 6 characters per field type designation, a single
ASCII record could come out to be a little longer than 25K characters.
Typical datalogger programming will produce record sizes of about 150
characters. It would not be unusual to see records that contain one or two
hundred values which would come out to a length of 2 to 3K characters in
ASCII.
To express the format of ASCII records used for communications between the
client and server, we will use Extended Backus Naur – Formalism (EBNF), a
notation used to express syntax. This notation was adopted from Wirth [3], and
extended here by adding a repetition count preceding some brackets. EBNF is
summarized in the following table where A, B and C are syntactic entities of
the language being described. Where one of these entities is a literal string it is
enclosed in quotes.
Expression Means
A = BC The construct A consists of B followed by C.
A = B | C A consists of B or C.
A = [B]
A consists of B or nothing.
A = {B} A consists of any number of B’s including none.
( ) Brackets used to group sections of an expression.
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