(BUG) OPC UA Server Generates Duplicate Monitored Item Notifications

(BUG) OPC UA Server Generates Duplicate Monitored Item Notifications

Hi there,

I've been working with the OPC UA server in Zenon recently as my company is using it for a project with a very high profile client. During analysis of the packet stream that Zenon generates when an OPC UA client has connected to it and subscribed to values (settings below), it was discovered that Zenon will generate duplicate notifications where only 1 data change actually occured.

First here's the subscription settings and monitored item settings that were used during the test:

* PublishingInterval = 500
* KeepAliveCount = 10
* LifetimeCount = 2400
* MaxNotificationsPerPublish = 1000
* PublishingEnabled = true
* TimestampsToReturn = Return both timestamps (server and source)

Monitored Items:
* AttributeId = Value
* SamplingInterval = 500
* QueueSize = 10
* DiscardOldest = true
* CacheQueueSize = 10
* Filter = Data Change Filter (which triggers on "StatusValue")
* MonitoringMode = Reporting

The image below of the wireshark capture shows the duplicate notifications in the PublishResponse from the Zenon OPC UA server:

Context: Only 1 value (a boolean) was changed from TRUE to FALSE, which should have only generated 1 MonitoredItem within the DataChangeNotification in the PublishResponse.

Any advice or feedback on Zenon's quirks, etc. is much appreciated as this is a major concern for a client of ours that is exploring using this protocol implementation at their data center. Within this context, wasteful network traffic is unacceptable.

Thanks for your time!

This is a migrated post! Originally posted on 02.07.2021 by user justinL. Please be aware that information can be outdated.