Events not notified when using StartNodeId != ObjectIds.Server

[Tiraflo]

Dear All,

I would like to receive events from a particular subset of the address space. So I started by modifying the boiler sample (BoilerNodeManager.cs) in order to send events periodically:

    private void DoSimulation(object state)
    {
        try
        {
            double value1 = m_boiler1.Drum.LevelIndicator.Output.Value;
            value1 = ((int)(++value1))%100;
            m_boiler1.Drum.LevelIndicator.Output.Value = value1;
            m_boiler1.ClearChangeMasks(SystemContext, true);

            double value2 = m_boiler2.Drum.LevelIndicator.Output.Value;
            value2 = ((int)(++value2))%20;
            m_boiler2.Drum.LevelIndicator.Output.Value = value2;
            m_boiler2.ClearChangeMasks(SystemContext, true);

            /* --- Added sources based on AlarmConditionNodeManager.cs --- */
            SystemEventState e = new SystemEventState(m_boiler1.Drum.LevelIndicator);

            e.Initialize(
                SystemContext,
                m_boiler1.Drum.LevelIndicator,
                EventSeverity.Medium,
                new LocalizedText("Raising Events Boiler 1"));

            e.SetChildValue(SystemContext, Opc.Ua.BrowseNames.SourceNode, m_boiler1.Drum.LevelIndicator.NodeId, false);
            e.SetChildValue(SystemContext, Opc.Ua.BrowseNames.SourceName, m_boiler1.Drum.LevelIndicator.DisplayName, false);

            Server.ReportEvent(e);
            /* --- */
        }
        catch (Exception e)
        {
            Utils.Trace(e, "Unexpected error during simulation.");
        }
    }

Then, on client's side, I create a monitored item according to the Boiler1/Drum/LevelIndicator object (after having browsed through nodes and found this particular one):

//Console.WriteLine("Subscribe to event for node {0}", ExpandedNodeId.ToNodeId(nextRd.NodeId, session.NamespaceUris));
Console.WriteLine("Subscribe to event for node {0}", nextRd.NodeId.ToString());
MonitoredItem monitoredItem = new MonitoredItem(subscription.DefaultItem) {
	DisplayName = nextRd.DisplayName.ToString(),
	//StartNodeId = ObjectIds.Server,
	StartNodeId = nextRd.NodeId.ToString(), // ExpandedNodeId.ToNodeId(nextRd.NodeId, session.NamespaceUris), 
	AttributeId = Attributes.EventNotifier
};
monitoredItems.Add(monitoredItem);
monitoredItem.NodeClass = NodeClass.Variable | NodeClass.Object;
monitoredItem.SamplingInterval = -1; // 0 ?
monitoredItem.QueueSize = 100;
monitoredItem.CacheQueueSize = 100;

The WriteLine call gives the following output:

Boiler #1, 2:Boiler #1, Object (ns=2;i=138)
' + Pipe1001, 2:PipeX001, Object (ns=2;i=139)
' + + + FTX001, 2:FTX001, Object (ns=2;i=140)
' + + + + Output, 2:Output, Variable (ns=2;i=141)
' + + + + + EURange, EURange, Variable (ns=2;i=144)
' + + + ValveX001, 2:ValveX001, Object (ns=2;i=147)
' + + + + Input, 2:Input, Variable (ns=2;i=148)
' + + + + + EURange, EURange, Variable (ns=2;i=151)
' + + + FTX001, 2:FTX001, Object (ns=2;i=140)
' + + + + Output, 2:Output, Variable (ns=2;i=141)
' + + + + + EURange, EURange, Variable (ns=2;i=144)
' + Drum1001, 2:DrumX001, Object (ns=2;i=154)
' + + + LIX001, 2:LIX001, Object (ns=2;i=155)
Subscribe to event for node ns=2;i=155
' + + + + Output, 2:Output, Variable (ns=2;i=156)
' + + + + + EURange, EURange, Variable (ns=2;i=159)
' + + + LIX001, 2:LIX001, Object (ns=2;i=155)

When setting StartNodeId to ObjectIds.Server, then I obtain this kind of notification:

LIX001: ByteString, System.Byte[]
LIX001: NodeId, i=2130
LIX001: NodeId, ns=2;i=155
LIX001: LocalizedText, LIX001
LIX001: DateTime, 23/04/2020 14:25:17
LIX001: DateTime, 23/04/2020 14:25:17
LIX001: Null,
LIX001: LocalizedText, Raising Events Boiler 1
LIX001: UInt16, 500

However, when setting StartNodeId to the desired node (ExpandedNodeId.ToNodeId(nextRd.NodeId, session.NamespaceUris or just nextRd.NodeId.ToString()) then I don't receive any notication anymore.

For info:

What did I misunderstand? What could be missing when Boiler 1/Drum/LevelIndicator is selected as the starting node?

Regards.

[11v1]

You calls ReportEvent on Server:
Server.ReportEvent(e);
From your server code it is not seen what variable "Server" is, but I suppose it is Server Node. If it so then that is the answer: you will receive events from the node that reports it or a "parent" node.

[Tiraflo]

Indeed, that's the server node (which I didn't noticed when "copying/pasting" from different samples...) and by replacing with the appropriate node (Boiler/Drum/LevelIndicator), I can now receive events when subscribing to this particular node.

In addition, if I properly understand, I can effectively receive events by subscribing to node's parent because the EventNotifier attribute and the HasNotifier reference are defined to allow it. Also, I can imagine that an event could have a SourceNode attribute which does not necessary match the node which report this event.

Thank you for your help.