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Pressure Systems, Inc. NetScanner™ System (9016, 9021, & 9022) User’s Manual
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transmissions in some operating modes (e.g., the hardware-triggered or free-run autonomous host
streams generated by the Configure/Control Autonomous Host Streams (‘c’) command).
A “peer” may be directly addressed by its IP address (in xxx.xxx.xxx.xxx format), or by use of a
predefined logical name that allows its IP Address to be looked-up in the sender’s database or in a
central network server’s database. The Windows
®
95/98/2000/NT operating systems provide a
simple text file database called “Hosts.” Review the file “Hosts.sam” in the “C:\windows” directory.
Modify and rename it “Hosts.” (no file extension) to activate it.
Before the host computer and any module can communicate with the higher level TCP/IP protocols,
the host (client) must request a connection be established with the module (server). Each module
expects all such requests for connection to be requested by its IP Address, and directed to “well-
known” port 9000 (default). After the connection is made, a socket is established as a logical handle
to this connection. The host and module may then communicate, via this socket, until it is closed
or is lost at either module or host end, due to power failure or reboot). The host and module may also
communicate in a limited fashion without a connection, using the middle-level UDP/IP protocols.
In that case, the host simply broadcasts commands via port 7000, and each module (that chooses to
respond) returns the response on port 7001. Only a few commands use UDP/IP in NetScanner
™
System modules.
3.1.2 Commands
The commands (and responses) used by Models 9016, 9021, and 9022 modules consist of short
strings of ASCII characters. The TCP/IP and UDP/IP protocols allow for the transfer of either
printable ASCII characters or binary data. When using certain formats, internal binary data values
are often converted to ASCII-hex digit strings externally. Such values may include the ASCII
number characters ‘0’ through ‘9,’ the uppercase ASCII characters ‘A’ through ‘F,’ and the
lowercase letters ‘a’ through ‘f’.’ These hex values may represent bit maps of individual options, or
actual integer or floating point (IEEE) binary data values. In other cases (see optional format 7
below) binary data may be transmitted directly as 4-byte (32-bit) binary values without any
formatting change. Such binary transmissions use big-endian (default) byte ordering but may be
commanded to use little-endian for some data.
3.1.2.1 General Command Format
A typical TCP/IP command (contained in the data field following a TCP packet header) is a variable-
length character string with the following general fields:
! a 1-character command letter (c).
! an optional position field (pppp), a variable length string of hexadecimal digits.
! a variable number of optional datum fields ( dddd): each a variable length string, normally
formatted as a decimal number (with a leading space character, and with or without sign