AVEVA Enterprise SCADA PubSub API Reference

Subscribe to and unsubscribe from a PubSub topic

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Subscribe to and unsubscribe from a PubSub topic

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Last UpdatedApr 08, 2026
1 minute read

HMI and SCADA

This scenario guides you through the steps required to subscribe to and unsubscribe from a PubSub topic.

To identify the code associated with each step, see the code comments in the Example code section.

To subscribe to and unsubscribe from a PubSub topic

Open the Program.cs file from the created project.
Open a PubSub connection.
Confirm there is a connection with the PubSub system.
Subscribe to a PubSub topic with a finite or non-finite timeout.
Receive data from the underlying PubSub connection. Data is blocked until available or the timeout has expired.
Unsubscribe from a PubSub topic by using one of the following methods:
- Using the Disconnect method.
```
// Disconnect, which will unsubscribe, clean up, and disconnect from the engine.
pubsubConnection.Disconnect();               
```
- Once the using block is finished, disposing the connection will remove the publisher, clean up, and disconnect from the engine. If a using block is used, calling Disconnect explicity is optional.

Example code

internal void AddSubscriptionWithConnectionFactoryAndUnsubscribe()
{
    try
    {
        IPubSubConnectionFactory pubSubConnectionFactory = new PubSubConnectionFactory();
        // Open a connection.
        using (var pubsubConnection = pubSubConnectionFactory.OpenConnection())
        {
            // Check if there is connection with the PubSub system.
            if (pubsubConnection.IsConnected())
            {
                var topic = "es.realtime.db.analog.DeviceRollupAnalog01.curval";
                // Subscribe to a PubSub topic with a finite or non-finite timeout.
                var subscription = pubsubConnection.Subscribe(topic, Timeout.InfiniteTimeSpan, true);
                 // Receive data from the underlying PubSub connection. Data is blocked until available or the timeout has expired.
                var pubsubMsg = subscription.Receive();                       
                Console.WriteLine(
quot;Current topic has: {pubsubMsg.GetDouble()} value.");
                // Unsubscribe from a PubSub topic.
                pubsubConnection.Disconnect();
            }
        }
    }
    catch (Exception ex)
    {
        Console.WriteLine("Error:" + ex.Message);
    }
}