title: OPC-UA server reboot and subscriptions
body: <p>In general, what happens: if a client has made a subscription on a OPC-UA node and this is functioning for some amount of time. The OPC-UA server publishes data to the client in standard behaviour. Then, the OPC-UA server reboots for any reason, do the OPC-UA store its subscribers and resumes the connection and continue to publish data after its startup? Or do the client need to sense that the server went down and thus recreate the subscription? If that is the case, should one generally use polling to achieve greater stability?</p>