Clarification of client reconnection event behaviour about opcuanet-samples HOT 1 CLOSED

Hi @JojoEffect,
thanks for opening this issue!

Your understanding is right that when ReconnectTimeout > 0 and the client loses connection to the server, the Reconnecting event is triggered, and the client automatically tries to establish a new connection to the server.

If the client is able to reconnect to the server, one of the following events will be raised:

• Reconnected will be raised if the session still exists at the server, and the client was able to reconnect to the existing session.
• Connected will be raised if the session no longer exists at the server, and the client has automatically created a new session.

In both cases, the client can be used again, and previously created subscriptions should still work. However, there are some differences:

• When Reconnected is raised, it means for subscriptions that you will get e.g. data changes that occured during the time while the client didn't have a connection to the server, because the session (and therefore the subscription) was still active at the server and collected data.
• When Connected is raised, the client had to re-create subscriptions on the server, which means e.g. data changes that occured during the time while the client didn't have a connection to the server will be lost (you will only get changes that occured after the client has created a new session).

Additionally, if you called OpcClient.RegisterNode(), then in case of Reconnected the node IDs will still work, but in case of Connected they will probably no longer work and you have to call OpcClient.RegisterNode() again.

In your example, you are restarting the server, so after the client can reconnect, the previous session will no longer exist on the server, which is why in this case Connected is always raised instead of Reconnected.

However, you are right that the documentation is a bit outdated and doesn't describe this difference, as this behavior was introduced with OPC UA .NET SDK version 2.12.0.0. Previously, the Reconnected event was raised in call cases after the Reconnecting event.
We will track this internally to update the documentation, so that it reflects the current behavior.

Thanks!

from opcuanet-samples.