Hello,

Please correct me if I am wroong here.

When we talk about the subscriptions and monitored items, a particular node is subscribed to by the client, and on the change of values in the node , the client is informed about the change, The information reaches the client at every publishing interval, and the node updates itself with the new value at every sampling interval.

Now, I have an OPC UA server which has analog signals. The values vary, and I can see the changing values on UA Expert.
I also have a test application using prosys java sdk, which tests if subscription functionality works fine or not. The code is as follows:

dataItem = new MonitoredDataItem(nid, Attributes.Value, MonitoringMode.Reporting, samplingInterval);
dataItem.setQueueSize(queueSize);
dataItem.setDiscardOldest(true);
dataItem.setDataChangeListener(listener);
s.addItem(dataItem);

Here, now from what I understand, if the value of the nid changes, then they are reported to the client. I sleep the program for 5 seconds to see the total number of changes in the listener. Works fine as the signals are changing.

However, i have another server which does not have varying signals( value is always a constant). Inspite of the constant value, the above chunk of code produces values for the listener.counter . Could you tell me how is it possible? Only if the value changes, the counter increments is my understanding. Please tell me if there are any other scenarios as well…