Hello,

So do we have to keep track of how long there is no response to conclude its dead? Or is there an event that tell there is no response for > some time say 20 secs or 30 secs.

If you want to monitor the status of subscription, see MySubscriptionAliveListener.onTimeout.

On the other hand, if you would like to monitor the status of the OPC UA server and not individual subscription, see MyServerStatusListener in the samples.

Hello,

To indicate that communication between client and server is live, the normal way in the SDK is to use the ServerStatusListener. In practice, the difference is that this will be more reliable and connection problems will be noticed quicker. Server status monitoring is done every statusCheckInterval. The default value of this statusCheckInterval is one second whereas noticing subscription timeouts takes MaxKeepAliveCount times PublishingInterval. Default value of MaxKeepAliveCount is 20 and for example with publishing interval of one second, that makes 20 seconds.

In principle, you can of course make a subscription with a small MaxKeepAliveCount and use that for server status monitoring. This however is more complicated than using the SDK default functionality and ServerStatusListener. You also most probably end up duplicating features already present in the SDK, such as automatic reconnecting.