6.3.5 Initial Connection, reconnecting, and ConfigurationChangedEvents

Components like audit collect may want to keep track of information of components of a Vending Machine, and potentially subcomponents. Therefore, when initially connecting to an OPC UA Server representing one or several components of a Vending Machine, those components need to browse and read the required information. For example, audit collect does need some information, to interpret the audit information. Therefore, it may need to browse the PaymentDevices and PaymentModes of the payment service. In order to keep track of changes of the configuration of components of a Vending Machine, the audit collect should subscribe to ConfigurationChangedEvents, and in case it receives such an Event re-browse and reread the information of that component. Although the configuration of a Vending Machine is typically quite static, it may be that at restart some devices like a bill validator take a much longer time to restart, and therefore get added to the configuration while the Vending Machine is already running.

When a component like audit collect is reconnecting to an OPC UA Server representing one or several components of a Vending Machine, there are two scenarios:

The connection could be re-established without loss of data. That means, the subscription is still running and the data indicate no loss of data. In that case, the component does not need to do any specific actions.

The connection could not be re-established or some losses of data have been indicated. In that case, the component needs to reread the information from the OPC UA Server.