Campbell Scientific LoggerNet Datalogger Support Software - Manual (Page 529)

Appendix D. Software Organization
D.1 LoggerNet/Client Architecture
The LoggerNet communication server provides the interface to all of the
dataloggers and the support for the different communications mediums. It runs
in the background and provides an attachment for the clients that provide the
user interface. The server handles all communications with the dataloggers.
The LoggerNet server handles connections from all the user interface screens
simultaneously, allowing many different views and ways to access the data
collected from the dataloggers. In addition to running on the same computer
with LoggerNet, the LoggerNetData applications can be run on other
computers connected to the LoggerNet computer over a local area network
(LAN).
LoggerNet can automatically collect data from the dataloggers on a schedule as
well as on request from the user. It can automatically check and update the
clocks in the dataloggers and handle administration support functions.
D.2 LoggerNet Server Data Cache
The LoggerNet server data cache is a set of files kept on the hard disk of the
computer where the server is running. These data files are in binary format and
can only be used or interpreted by the LoggerNet server. The data cache files
are stored in addition to the output data files.
D.2.1 Organization
The data cache is set up to emulate the way data is stored in the datalogger.
When a new datalogger station is defined for the network and communication
is established with the station, the server requests the table definitions from
table data dataloggers. For array based dataloggers the array definitions are
contained in a final storage label file that is associated with a datalogger. This
table or array information is used to set up equivalent tables and data arrays for
data storage in the data cache. The size of the areas set up in the data cache is
dependent on the size of final storage in the datalogger.
Datalogger tables that hold only one record, such as the Input Locations table
and the Status table, would have only two records assigned in the data cache.
The storage in the data cache is designed to operate with “ring memory” just
like the datalogger. This means that records will be stored in the data cache
area for that table until it has reached the maximum number of records, the next
data record will replace the oldest record in the storage table, and so on.
D.2.2 Operation
Normal data collection from the datalogger is done with polling based on the
scheduled collection interval set up by the user. This is the most efficient
means of data collection for networks with rapid direct communications links.
When it is time for a scheduled data collection the server sends a data poll
request to the datalogger to get all of the data stored in the selected tables since
D-1