Campbell Scientific LoggerNet Datalogger Support Software - Manual (Page 443)

Section 11. Utilities Installed with LoggerNet Admin and LoggerNet Remote
the unsent records remain in the LoggerNet server’s data cache. The Data
Export maintains transfer progress information on disk so that if the server
goes down or there is another problem with the transfer, it can recover and
continue to transfer all collectable records.
The record acknowledgment allows Data Export to ensure that every record it
intended to send was successfully received by the client. This capability,
coupled with reasonable algorithms that make sure the LoggerNet server
receives every record logged by the datalogger, allows for reliable data
collection.
11.4.3 Custom Data Retrieval Client
Because there are so many different types of database applications and data
handling processes in use, the data retrieval client must be created either by the
customer or on contract with Campbell Scientific to the custom specifications
of the user’s process.
The custom data retrieval client is a software application that connects to the
socket provided by the Data Export application. It can be programmed to run
on any computer platform that is configured to support TCP/IP as long as there
is a computer network connection available to the host computer where the
Data Export application is running.
When a connection is established, the Data Export will send one data record as
soon as it is available. The first data record sent depends on the Data Export
option settings.
When the data retrieval client receives the record, it must parse the data and
return the acknowledgment message to the Data Export. The acknowledgment
message consists of the name of the datalogger, the name of the table, and the
record number of the record received.
If the acknowledgment message is not returned within 60 seconds or if the
message is incorrect, the Data Export will re-send the same record again. It
will continue sending the same record at 60-second intervals until either the
connection is broken or a valid acknowledgment for that record is received.
The custom data retrieval client is programmed to write to the database or file
system defined for the user’s data handling process.
11.4.4 Custom Client/Data Export Interface Description
This section details the interface for writing a custom data retrieval client that
will get data from the Data Export application. The programming concepts
presented assume a familiarity with programming software applications to
connect with a TCP/IP socket.
The Data Export application functions as a server providing a TCP/IP socket
connection for one remote client. Once the Data Export has connected to the
LoggerNet communication server the TCP/IP socket is established and the
Data Export application starts “listening” for a client to attach. As soon as a
data retrieval client connection is detected the Data Export application sends
the first record out over the socket connection. Upon receiving the record the
data retrieval client needs to send back an acknowledgment message consisting
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