Subscribe to a topic

Private Sub Subscribe()
On Error GoTo errExit
    Dim retCode As MqttSubscriptionCode
    Dim subOption As MQTTSubscribeOption
    
    Set subOption = mFactory.CreateSubscribeOption
    subOption.QoS = MqttQoS2
    subOption.Identifier = 10
    subOption.Topic = "SE"
    
    retCode = mClient.Subscribe(subOption)
    Exit Sub
    
errExit:
    MsgBox err.Description
End Sub