Develop the subscriber NetLogic and interface

Develop a NetLogic and integrate it with the interface.

Develop the NetLogic

Right-click MainWindow (type) and select New > Runtime NetLogic.
Hover-over the NetLogic, select , and enter SubscriberLogic.
Double-click the NetLogic.
The external code editor opens.

In the code editor, replace the existing code with the following code:

#region StandardUsing
using System;
using FTOptix.CoreBase;
using FTOptix.HMIProject;
using UAManagedCore;
using OpcUa = UAManagedCore.OpcUa;
using FTOptix.NetLogic;
using FTOptix.UI;
using FTOptix.OPCUAServer;
#endregion
using uPLibrary.Networking.M2Mqtt;
using uPLibrary.Networking.M2Mqtt.Messages;

public class SubscriberLogic : BaseNetLogic
{
    public override void Start()
    {
        var brokerIpAddressVariable = Project.Current.GetVariable("Model/BrokerIpAddress");

        // Create a client connecting to the broker (default port is 1883)
        subscribeClient = new MqttClient(brokerIpAddressVariable.Value);
        // Connect to the broker
        subscribeClient.Connect("SubscriberClient");
        // Assign a callback to be executed when a message is received from the broker
        subscribeClient.MqttMsgPublishReceived += SubscribeClientMqttMsgPublishReceived;
        // Subscribe to the "my_topic" topic with QoS 2
        ushort msgId = subscribeClient.Subscribe(new string[] { "/my_topic" }, // topic
            new byte[] { MqttMsgBase.QOS_LEVEL_EXACTLY_ONCE }); // QoS level

        messageVariable = Project.Current.GetVariable("Model/Message");
    }

    public override void Stop()
    {
        subscribeClient.Unsubscribe(new string[] { "/my_topic" });
        subscribeClient.Disconnect();
    }

    private void SubscribeClientMqttMsgPublishReceived(object sender, MqttMsgPublishEventArgs e)
    {
        messageVariable.Value = "Message received: " + System.Text.Encoding.UTF8.GetString(e.Message);
    }

    private MqttClient subscribeClient;
    private IUAVariable messageVariable;
}

Save the code.

Create the interface elements

Create the message variable by performing the following actions:
1. In Project view, right-click Model and select New > Variable.
2. Hover-over the variable, select , and enter Message.
3. In Properties, select Int32 and select String.
Create the Subscribe label by performing the following actions:
1. In Project view, right-click MainWindow (type) and select New > Base controls > Label.
2. Hover-over the label, select , and enter SubscribeLabel.
3. In Properties, create a dynamic link between Text and the Message variable.
  
  For more information about dynamic links, see Create dynamic links.
Arrange the interface elements.