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Implement subscription mechanism

Soaib Safi

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Forum Posts: 2

Member Since:
09/21/2020

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09/21/2020 - 04:40

I’m having trouble with OPC UA Subscriptions and Notifications. I want to subscribe server data. So I defined a monitoredItem list to capture the notification.


var subscription = new Subscription(session.DefaultSubscription) { PublishingInterval = 1000 };
var list = new List<MonitoredItem> {
        new MonitoredItem(subscription.DefaultItem) { DisplayName = "Speed", StartNodeId = "ns=2;i=4"},
    };
Debug.Log(list[0].StartNodeId);
list.ForEach(i => i.Notification += OnNotification);
subscription.AddItems(list);
list.ForEach(i =>  Debug.Log(i.Subscription.Id));

When ever it get new notification, it suppose to call the OnNotification deligate. But it my case the OnNotification is never be called.



private static void OnNotification(MonitoredItem item, MonitoredItemNotificationEventArgs e)
{
        Debug.Log("OnNotification");
        foreach (var value in item.DequeueValues())
        {
            Debug.LogFormat("{0}: {1}, {2}, {3}", item.DisplayName, value.Value, value.SourceTimestamp, value.StatusCode);
        }
}

How can I implement subscription mechanism in this case? Cry

Randy Armstrong

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Forum Posts: 1580

Member Since:
05/30/2017

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09/21/2020 - 10:18

There are many potential issues:

1) Subscription is disabled;

2) Subscription has not been created;

3) CreateMonitoredItems was not called;

4) MonitoringMode != Reporting;

5) The event on the subscription object has not been subscribe to.

Soaib Safi

New Member

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Forum Posts: 2

Member Since:
09/21/2020

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09/25/2020 - 01:56

Here is what I have done till now. Could you please tell me what else I need to change in my code?

Debug.Log(“Step 4 – Create a subscription. Set a faster publishing interval if you wish.”);
var subscription = new Subscription(session.DefaultSubscription) { PublishingInterval = 1000 };

Debug.Log(“Step 5 – Add a list of items you wish to monitor to the subscription.”);
var list = new List<MonitoredItem> {
new MonitoredItem(subscription.DefaultItem) { DisplayName = “Speed”, StartNodeId = “ns=2;i=2”},
};
Debug.Log(list[0].StartNodeId);
list.ForEach(i => i.Notification += OnNotification);
subscription.AddItems(list);
list.ForEach(i => Debug.Log(i.Subscription.Id));
subscription.PublishingEnabled = true;

Debug.Log(“Step 6 – Add the subscription to the session.”);
session.AddSubscription(subscription);
subscription.Create();

Debug.Log(“Finished client initialization”);
Console.WriteLine(“Finished client initialization”);