NodeId Question

[shauney]

Hello, I have a question about NodeIds.

I want to use the device set nodes so I am loading in the xml file from
http://opcfoundation.org/UA/schemas/DI/ ... deSet2.xml

In this XML file it specifies the node Id of the device set is "ns=1;i=5001"
When I create a model in UaModeler and load in the Device set model it also shows the Device Set Node Id as "1:5001".

I then tried to get the node in my code with .getNode(new NodeId(1, 5001)); and this failed.
When I browsed my server with UaExpert I saw that the Device Set Node Id was "2:5001" and I could get the node in my server code with .getNode(new NodeId(2, 5001));

Now I understand from another forum post that NodeIds can change when the server is restarted or other nodes are added but how then do I lookup the DeviceSet node or other nodes from my server code when I cannot rely on the NodeId?

Thankyou for your help.
Shaun

[Support Team]

Hello Shauney,

The Server will have a NamespaceArray below the "Server" node, this is fixed on NS=0 (OPCFoundation namespace), which every UA Server must have. In this array you will find the mapping of NamespaceURI and NamespaceIndex. Therefore a Client should never persist (or hard code) any NamespaceIndex, you always need to resolve the mapping again when connecting to the particular Server a second time. The only namespace you can rely on being at the same index every time is the NS=0.

With the UaModeler the DI namespace and the PLCopen and maybe other "companion" standard namespaces, are typically treated different because they are "in-built" in the SDK (and the known to UaModeler). With the UaModeller you would normally create "your own" model, rather that create models that already exist.

Best Regards
Support Team