Echelon OpenLDV - Manual (Page 141)

OpenLDV Programmer’s Guide 133
• Windows Vista or Windows 7: \Users\Public\Documents
\LonWorks\OpenLDV SDK\xDriver API Examples
• Windows XP: \Documents and Settings\All Users\Documents
\LonWorks\OpenLDV SDK\xDriver API Examples
The example applications are also installed as a ZIP file in the L ON W ORKS
\OpenLDV SDK\SourceArchive folder on your computer. The ZIP file is
named xDriverApiExamplesSource_vn.nn.nnn.ZIP file (where n.nn.nnn
represent the current version and build of the OpenLDV SDK).
The C++ sample program uses a comma-separated variable (CSV) file as its
database to store the SCO information for the lookup extension. Because the
database is a CSV file, the sample program uses standard file I/O methods for
managing the database.
The Visual Basic sample program uses ADO.NET to connect to a database that
stores the information that the lookup extension must fill into the SCO each time
an xDriver connection is initiated. It retrieves this information from the
database using standard ADO techniques, and uses the properties and methods
of the xDriver type library to fill this information into the SCO.
ADO.NET can use either SQL or OLE connections to access a database. In
general, you use only one connection type to access your database, but this
sample is coded to implement either connection type on a per-session basis.
Comments are included within the programming sample to provide further
guidance.
If you are using an LNS Server, for a downlink session, the sample lookup
extension component is launched by an LNS application after the System object
for the remote network is opened. The New() function is called first. The
SetInstance and the SetOptions functions are called next to initialize the SCO
with any user-defined parameters. If parameters are not specified, predefined
defaults are used. The DownlinkLookup() function is then called by the
xDriver manager automatically, and the downlink lookup key is extracted from
the passed-in SCO. The downlink lookup key is used to locate the database record
for the RNI. The UpdateSCO() helper function, which extracts the required
fields from the located database record and fills them into the SCO, is then
called.
If you are using an LNS Server, for an uplink session, the sample lookup
extension component is launched when the uplink session request is received by
the LNS Server. The New() function is called first. The SetInstance and the
SetOptions functions are called next to initialize the SCO with user-defined
parameters. If parameters are not specified, predefined defaults are used. The
UplinkLookup() function is then called by the xDriver automatically, and the
uplink lookup key is extracted from the passed-in SCO. The uplink lookup key is
used to locate the database record for the RNI that has requested the uplink
session. The UpdateSCO() helper function, which extracts the required fields
from the located database record and fills them into the SCO, is then called.
The UpdateLookup function is called after the SCO has been filled in during an
xDriver session if the current and next authentication keys filled in differ, which
indicates that a change to the authentication key used by the RNI is required.
The UpdateLookup function must be coded to implement an update to the
xDriver database to reflect this change. The xDriver database must always store
the correct values of the current and next authentication keys for an RNI, and