Echelon LNS - Manual (Page 240)

LNS Programmer's Guide 226
To monitor messages that begin with a specific message code, set the
FilterByCode
monitoring options property to True, and the
FilterCode
property to the message code
to be monitored when you set the monitoring options for the monitor set.
To recap this discussion, follow these steps to monitor messages:
1. Create a monitor set, and add monitor points for the message tags you
want to monitor. For more information on these tasks, see Creating
Monitor Sets on page 194, and Managing Monitor Sets on page 195.
2. Connect one or more devices to the host PC, and add corresponding
message monitor points to the monitor set as described in the Adding
Message Monitor Points to a Monitor Set section on page 197. In the case
where a remote device propagates an explicitly addressed message with
an appropriate destination address, no such connection will be required.
3. Open and enable the monitor set, as described in Opening and Enabling
Monitor Sets on page 213.
4. Use the
OnMsgMonitorPointUpdateEvent
event to monitor the
message monitor points. An example event handler for the
OnMsgMonitorPointUpdateEvent
event is shown below.
Receiving Message Monitor Point Updates
Once you have opened and enabled your message monitor points, your application will
begin receiving
OnMsgMonitorPointUpdateEvent
events each time a message is sent
to the monitored devices via your message tags. The
OnMsgMonitorPointUpdateEvent
event returns the message monitor point that caused the event to be fired, and a
SourceAddress
object identifying the device containing the message point. It also
returns two
DataPoint
objects:
inputDataPoint
and
outputDataPoint
.
inputDataPoint
contains the information that was received from the monitored point.
If the incoming message is a request message, you can use the
outputDataPoint
parameter to return a response.
Note that Echelon discourages using the
SourceAddress
object to identify the source of
a message. It is more efficient to set the FilterByAddress property of the message tag
to True, and rely on the message tag to identify the sending device.
Example Message Monitor Point Event Handler
The following code example shows how the OnMsgMonitorPointUpdateEvent could be
used to return data to an external device that requested such data using the
request/response messaging service This event handler checks the name of the message
monitor point to determine which device sent the message, and if the message is a
request it then sends a response to the request.
Note that by using the
OnMsgMonitorPointUpdateEvent
event as described in these
sections, you will receive the events through the LNS Object Server. If your development
environment supports multi-threading, you can use the
ILcaMsgMonitorPointListener interface to receive the events directly from the
message monitor point. For more information on this, see Tracking Monitor Point
Updates on page 228.