View Full Version : (BUG) OPC UA Server Generates Duplicate Monitored Item Notifications

2nd July 2021, 14:03
Hi there,<br><br>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.<br><br>First here's the subscription settings and monitored item settings that were used during the test:<br><br><div><div><strong>Subscription:</strong></div><div>* PublishingInterval = 500</div><div>* KeepAliveCount = 10</div><div>* LifetimeCount = 2400</div><div>* MaxNotificationsPerPublish = 1000</div><div>* PublishingEnabled = true</div><div>* TimestampsToReturn = Return both timestamps <em>(server and source)</em><br><br><div><strong>Monitored Items:</strong></div><div>* AttributeId = Value</div><div>* SamplingInterval = 500</div><div>* QueueSize = 10</div><div>* DiscardOldest = true</div><div>* CacheQueueSize = 10</div><div>* Filter = Data Change Filter <em>(which triggers on "StatusValue")</em></div><div>* MonitoringMode = Reporting</div></div></div><br>The image below of the wireshark capture shows the duplicate notifications in the <strong>PublishResponse</strong> from the Zenon OPC UA server:<br><br><img src="https://forum.copadata.com/attachment.php?attachmentid=3136&amp;stc=1" attachmentid="3136" alt="" id="vbattach_3136" class="previewthumb"><br><br>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.<br><br>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.<br><br>Thanks for your time!<br>-Justin

22nd July 2021, 07:48
<em>as this is not an energy specific topic, i'm moving&nbsp;you post to another node (maybe this will increase your chances to attract the attention of an OPC UA expert).</em>