I connected an OPC UA device and tried to access the tags in the designer, but noticed that they had no value displaying in the tag browser. I then went to the OPC quick client and found that I could do single reads of the tags and get correct values. However, I can't subscribe to them or use them in the designer like this. I checked the connection at the device's end, and it all looks normal and nothing is errored. Is there some kind of setting that would disable this in ignition? or is it possible that a device would only allow a single subscription? The device is reporting the tags to a Canary Historian via OPC UA successfully.
Also, I am on Ignition version 8.1.32 and I am connecting to a B&R X20 CP 3584 PLC that sends its tags to a B&R Automation PC 2100 that publishes OPC UA.
Nothing on the Ignition side that would account for this...
It would be useful for you to make that OPC connection without security and then get a Wireshark capture of the connect + subscription and monitored item creation happening.
Hi Kevin,
Thanks for the help. I mirrored the traffic and got a wireshark capture of the packets while I attempted to create a subscription to one of the tags in the OPC Quickclient. My ignition instance is running on 192.168.40.68 and the PC publishing the tags is on 192.168.40.59. I can't quite see anything that looks like an error, but I don't have experience with looking at OPC UA on this level. I tried creating a subscription on another OPC UA device that I know I can subscribe to, and it looked almost identical. The only difference that I could see between the two is that the successful subscription only had to send one set of "SetMonitoringModeRequest" and "Response" packets while the PC where subscriptions are not working had to do that twice (in the picture below).
Also, I know you said to do the capture without security, and I don't have any certificates on either machine, but the wireshark capture still says "secure conversation" and I don't know why.
Can you upload the capture somewhere?
Sure, does this work? I couldn't get the capture filters to work so if you open it up and filter for OPC UA it is the only traffic.
subscribeAttempt.zip (6.3 MB)
Hmm, I think you might need to contact Beckhoff for support, or start with a firmware upgrade if something like that is available.
We create the Monitored Item and it get assigned an id of 303:
Then in the subsequent attempt call to SetMonitoringMode the server thinks it doesn't exist:
Some clients create the items in MonitoringMode.Reporting to being with, some create them in Disabled or Sampling mode and then flip them to Reporting when ready. Ours does the latter, which is why the SetMonitoringMode calls appear.
I contacted the supplier and they said they would have to look into the source code for the OPC server, but in the meantime, I was able to get values and use the tags via a read at set polling rate instead of a subscription. Thanks for the help!
