Event Subscription in OPC-UA till Client Application does not close.

[codekundan]

Hi Plc4x Team, I am writing a JavaFX application in which I want to read Tags values especially BOOL ones to trigger fetching from Database and pass the values to PLC. I am able to get the Events but point is I want it for indefinite time till the user does not close the JavaFX Application. After few hours, there is no response from Event change. Any help regarding to make Event Subscription for long periods of time as much as possible ?

`package com.example.scadademo;

import javafx.concurrent.Task;
import org.apache.plc4x.java.DefaultPlcDriverManager;
import org.apache.plc4x.java.api.PlcConnection;
import org.apache.plc4x.java.api.exceptions.PlcConnectionException;
import org.apache.plc4x.java.api.exceptions.PlcRuntimeException;
import org.apache.plc4x.java.api.messages.PlcSubscriptionResponse;

import java.util.concurrent.CompletableFuture;

public class EventSubscriptionTask extends Task {
@OverRide
protected Void call() throws Exception {
new EventSubscriptionTask().plcFunc();
return null;
}

private void plcFunc() {
    String connectionString = "opcua:tcp://LAPTOP-A1865M3M:4841?discovery=true&security-policy=Basic128Rsa15&message-security=SIGN_ENCRYPT&key-store-file=test-mxopc-keystore.p12&key-store-password=user_password";

    try (PlcConnection connection = new DefaultPlcDriverManager().getConnection(connectionString)) {
        System.out.println("Conenction made....................");
        CompletableFuture<? extends PlcSubscriptionResponse> future = connection.subscriptionRequestBuilder()
                .addChangeOfStateTagAddress("c", "ns=4;s=Address Space.Dev00.Tag000")
                .build().execute();
        future.whenComplete((r, e) -> {
            if (e != null) {
                e.printStackTrace();
                return;
            }
            r.getSubscriptionHandle("c").register(event -> {
                for (String field : event.getTagNames()) {
                    System.out.println("Received state update: " + field + " " + event.getObject(field) + " " + event.getResponseCode(field));
                }
            });
        }).get();

      //Added while loop so that Event subscription does not terminate. It ends when 
     // main Application EventSubscription ends making closingFlag property true.
        while(!EventSubscription.closingFlag) {
          Thread.sleep(2000);
            System.out.println("background thread running...................");
        }
        System.out.println("Closing connection");
    } catch (PlcConnectionException e) {
        throw new PlcRuntimeException(e);
    } catch (Exception e) {
        e.printStackTrace();
    }
}

}
`