V8.1.0 Null pointer exception in OPC Server diagnostics for Rx3i PLC

This is on a fresh install of v8.1.0 running on Ubuntu (and running on a VirtualBox VM)

I just made an OPC connection to my local Rx3i CPE305 based system. On the gateway the status is marked as “Connected”, but when I click on the “Server Diagnostics” I get an error message for a Null pointer exception:

Error { “servlet”:“DataRoutes”, “message”:“java.lang.NullPointerException: diagObjectBrowse.references must not be null”, “url”:"/data/opc-ua/status/diagnostics/TESTLOCALPLC1/sessions", “status”:“500” }


  1. I get valid data when I clicked on the Server Diagnostics for the Ignition OPC UA Server
  2. I can successfully connect to the same PLC using the free Matrikon OPC UA Explorer and see all sorts of diagnostic data there

Here are some pretty pictures of my setup and the issue:

Thanks, I think this is probably easy to fix. If I build and upload an OPC UA module in a bit here would you be able to verify the fix against this server?

Yes I am happy to help to get things fixed!

Okay, try installing this OPC UA module and see if anything changes.

That fixed the problem

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Now for the big question. When will this fix likely make it to an official release?

It will be part of 8.1.2.

A nightly release that is basically no more official than the module I just gave you will be available sooner, but the final release of 8.1.2 is sometime in January.

I have a customer deadline for the end of January … so that should work out great!

Now I’m going to surprise my colleagues (again!) with the fact that I reported and got a solution to a genuine bug in an hour. Not like some other HMI providers that work at a glacial pace :wink:

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Sometimes you get lucky, other times not as much… :slight_smile:


I’m currently having the exact same error with 8.0.16 and a Van Dorn (Injection Molding Machine) which runs an S3 (SigmaTek) OPC-UA server.

Coincidentally enough, we started having issues with the subscription dropping and the server refusing to forward the sub. I’m admittedly out of my depth on most of this.

Thanks in advance

I don’t think the two things are related. You’ll have to upgrade to 8.1.1 if you want to test this module and see if it allows you to access the status page.

Troubleshooting the subscription dropping will require a bit more information: logs, maybe Wireshark captures, etc… and is probably more appropriate for a new topic.

Thanks for the quick reply. I will start a new topic if the issue persists over the weekend.