Echelon LNS - Manual (Page 242)

LNS Programmer's Guide 228
connected to the PC running the application. Independent client applications read and
write data directly to and from the devices on the network without writing to the LNS
database.
Temporary
MonitorSets
objects are not available to Independent client applications,
and neither are the methods and properties of the
AppDevice
object. However,
Independent client applications have access to all permanent monitor sets and monitor
points (note that the LNS Server must be present in order to create monitor points).
This means that an Independent client application on a PC with monitor sets defined in
its
CurrentMonitorSets
collection can open those monitor sets and use them for
monitor and control operations without being attached to the LNS Server. Independent
client applications can configure existing monitor points and sets using the
CurrentOptions
(but not the
NvOptions
or MsgOptions properties of a MonitorSet,
or the DefaultOptions property of an individual monitor point), and enable the
monitor points, but no other network functionality is available.
To open a network in independent mode and perform monitor and control operations, the
remote PC must have previously accessed the network as a Full client in server-
dependent mode, and created one or more monitor sets using the
MonitorSets
collection
accessed through the
MyVNI
property. After this, an Independent client application on
the PC can open the network and the monitor points can be monitored and controlled.
For more information on Independent clients and server-independent mode, see
Independent Clients on page 41. For more information on the differences between the
MonitorSets
collections accessed through the
MyVNI
and
CurrentMonitorSets
properties, see Permanent Monitor Sets on page 192.
Tracking Monitor Point Updates
This chapter describes several ways you can use the
OnMsgMonitorPointUpdateEvent
and
OnNvMonitorPointUpdateEvent
events to track updates to your monitor points.
You will receive these event updates through the LNS Object Server. Alternatively, you
can receive these events directly through the monitor points using the
ILcaMsgMonitorPointListener and ILcaNvMonitorPointListener interfaces.
Using these interfaces results in improved LNS application performance, and provides
update and error events in a separate thread. The application remains responsive, and
all updates and error logging occurs in the background. This technique can only be used
if your development environment supports multi-threading (such as Visual C++). You
cannot use this technique with Visual Basic 6.0.
For more information on multi-threading and LNS, see Multi-Threading and LNS
Applications on page 318.
To use the ILcaMsgMonitorPointListener interface, follow these steps:
1. Create a COM object that implements the
ILcaMsgMonitorPointListener interface.
2. Define the object's behavior when the UpdateErrorEvent() and
UpdateEvent() methods are called. These methods will be called each
time the monitor point you select in step 3 is updated.