UascClientAcknowledgeHandler trying to make a connection with server when the certificate info is wrong.

[sc-sityad]

UascClientAcknowledgeHandler tries to make a connection with server when the client info is wrong, So I call the disconnect() method.
But still it tries to connect which makes the unwanted traffic on the server if multiple clients wants to connect with let say wrong client info. The neo threads infinitely ping the server for the connection. The error logs that occured:

`2024-03-15 22:58:18.998 ERROR 2392986 --- [ty-event-loop-5] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
Failed to connect to OPC UA server.
2024-03-15 22:58:19.002 INFO 2392986 --- [nio-9002-exec-5] com.neos.opcua.service.OpcuaService : com.neos.opcua.exception.OpcuaException: Failed to connect to OPCUA server
java.util.concurrent.ExecutionException: java.lang.RuntimeException: Failed to connect to OPC UA server.

com.neos.opcua.exception.OpcuaException: Failed to connect to OPCUA server
java.util.concurrent.ExecutionException: java.lang.RuntimeException: Failed to connect to OPC UA server.
at com.neos.opcua.service.OpcuaService.open(OpcuaService.java:153) ~[classes!/:0.0.1-SNAPSHOT]
at com.neos.opcua.service.OpcuaService.testConnection(OpcuaService.java:132) ~[classes!/:0.0.1-SNAPSHOT]
at com.neos.opcua.controller.Controller.testConnection(Controller.java:77) [classes!/:0.0.1-SNAPSHOT]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_281]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_281]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_281]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_281]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:197) [spring-web-5.3.6.jar!/:5.3.6]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:141) [spring-web-5.3.6.jar!/:5.3.6]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106) [spring-webmvc-5.3.6.jar!/:5.3.6]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:894) [spring-webmvc-5.3.6.jar!/:5.3.6]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) [spring-webmvc-5.3.6.jar!/:5.3.6]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) [spring-webmvc-5.3.6.jar!/:5.3.6]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1060) [spring-webmvc-5.3.6.jar!/:5.3.6]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:962) [spring-webmvc-5.3.6.jar!/:5.3.6]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) [spring-webmvc-5.3.6.jar!/:5.3.6]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) [spring-webmvc-5.3.6.jar!/:5.3.6]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:626) [tomcat-embed-core-9.0.45.jar!/:na]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) [spring-webmvc-5.3.6.jar!/:5.3.6]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) [tomcat-embed-core-9.0.45.jar!/:na]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227) [tomcat-embed-core-9.0.45.jar!/:na]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) [tomcat-embed-core-9.0.45.jar!/:na]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) [tomcat-embed-websocket-9.0.45.jar!/:na]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) [tomcat-embed-core-9.0.45.jar!/:na]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) [tomcat-embed-core-9.0.45.jar!/:na]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) [spring-web-5.3.6.jar!/:5.3.6]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.3.6.jar!/:5.3.6]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) [tomcat-embed-core-9.0.45.jar!/:na]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) [tomcat-embed-core-9.0.45.jar!/:na]
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) [spring-web-5.3.6.jar!/:5.3.6]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.3.6.jar!/:5.3.6]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) [tomcat-embed-core-9.0.45.jar!/:na]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) [tomcat-embed-core-9.0.45.jar!/:na]
at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.java:93) [spring-boot-actuator-2.4.5.jar!/:2.4.5]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.3.6.jar!/:5.3.6]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) [tomcat-embed-core-9.0.45.jar!/:na]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) [tomcat-embed-core-9.0.45.jar!/:na]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) [spring-web-5.3.6.jar!/:5.3.6]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.3.6.jar!/:5.3.6]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) [tomcat-embed-core-9.0.45.jar!/:na]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) [tomcat-embed-core-9.0.45.jar!/:na]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) [tomcat-embed-core-9.0.45.jar!/:na]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) [tomcat-embed-core-9.0.45.jar!/:na]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542) [tomcat-embed-core-9.0.45.jar!/:na]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143) [tomcat-embed-core-9.0.45.jar!/:na]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.45.jar!/:na]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) [tomcat-embed-core-9.0.45.jar!/:na]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357) [tomcat-embed-core-9.0.45.jar!/:na]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374) [tomcat-embed-core-9.0.45.jar!/:na]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core-9.0.45.jar!/:na]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:893) [tomcat-embed-core-9.0.45.jar!/:na]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1707) [tomcat-embed-core-9.0.45.jar!/:na]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.45.jar!/:na]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_281]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_281]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.45.jar!/:na]
at java.lang.Thread.run(Thread.java:748) [na:1.8.0_281]

2024-03-15 22:58:19.003 INFO 2392986 --- [nio-9002-exec-5] com.neos.opcua.service.OpcuaService : Close connection
2024-03-15 22:58:19.003 INFO 2392986 --- [nio-9002-exec-5] com.neos.opcua.Handler.OpcuaHandler : Client is disconnected.
2024-03-15 22:58:20.014 ERROR 2392986 --- [ty-event-loop-6] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 22:58:22.032 ERROR 2392986 --- [ty-event-loop-7] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 22:58:26.047 ERROR 2392986 --- [ty-event-loop-8] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 22:58:34.062 ERROR 2392986 --- [ty-event-loop-9] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 22:58:50.077 ERROR 2392986 --- [y-event-loop-10] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 22:59:06.092 ERROR 2392986 --- [y-event-loop-11] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 22:59:22.109 ERROR 2392986 --- [y-event-loop-12] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 22:59:38.123 ERROR 2392986 --- [y-event-loop-13] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 22:59:54.139 ERROR 2392986 --- [y-event-loop-14] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 23:00:10.157 ERROR 2392986 --- [y-event-loop-15] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 23:00:26.172 ERROR 2392986 --- [ty-event-loop-0] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 23:00:42.185 ERROR 2392986 --- [ty-event-loop-1] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 23:00:58.199 ERROR 2392986 --- [ty-event-loop-2] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 23:01:14.213 ERROR 2392986 --- [ty-event-loop-3] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 23:01:30.227 ERROR 2392986 --- [ty-event-loop-4] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 23:01:46.242 ERROR 2392986 --- [ty-event-loop-5] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 23:02:02.257 ERROR 2392986 --- [ty-event-loop-6] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 23:02:18.271 ERROR 2392986 --- [ty-event-loop-7] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 23:02:34.285 ERROR 2392986 --- [ty-event-loop-8] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 23:02:50.300 ERROR 2392986 --- [ty-event-loop-9] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 23:03:06.314 ERROR 2392986 --- [y-event-loop-10] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 23:03:22.328 ERROR 2392986 --- [y-event-loop-11] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 23:03:38.343 ERROR 2392986 --- [y-event-loop-12] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 23:03:54.357 ERROR 2392986 --- [y-event-loop-13] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 23:04:10.372 ERROR 2392986 --- [y-event-loop-14] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 23:04:26.386 ERROR 2392986 --- [y-event-loop-15] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 23:04:42.399 ERROR 2392986 --- [ty-event-loop-0] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 23:04:58.414 ERROR 2392986 --- [ty-event-loop-1] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 23:05:14.428 ERROR 2392986 --- [ty-event-loop-2] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 23:05:30.442 ERROR 2392986 --- [ty-event-loop-3] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 23:05:46.455 ERROR 2392986 --- [ty-event-loop-4] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 23:06:02.469 ERROR 2392986 --- [ty-event-loop-5] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
2024-03-15 23:06:18.485 ERROR 2392986 --- [ty-event-loop-6] m.o.s.c.t.u.UascClientAcknowledgeHandler : [remote=/10.149.10.66:4841] Received error message: ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=[BadSecurityChecksFailed]}
`

If u see the logs I call disconnect() on the client . but after that also it tries again and again.

[sc-sityad]

@kevinherron Can u guide me. I had call the disconnect() on client. After that also it continously tries to connect to server.(some kind of event thread pool which did not stop after the client is disconnected. For refereence my code looks like

public static CompletableFuture<OpcUaClient> connect(String host, Integer port, String username, String password,
                                                     String certPath, String keyPath, String applicationUri, String securityPolicy, String messageSecurity) {
    return createClient(host, port, username, password, certPath, keyPath, applicationUri, securityPolicy,messageSecurity)
            .thenCompose(OpcUaClient::connect).thenApply(OpcUaClient.class::cast);
}

private static CompletableFuture<OpcUaClient> createClient(String host, Integer port, String username,
                                                           String password, String certPath, String keyPath, String applicationUri, String securityPolicy, String messageSecurity) {
    // create URL
    String url = String.format("opc.tcp://%s:%s", host, port);

    return DiscoveryClient.getEndpoints(url).thenCompose(endpoints -> {
        try {
            // fetch EndpointDescription
            EndpointDescription endpointDescription = findBest(endpoints);
            MessageSecurityMode messageSecurityMode = endpointDescription.getSecurityMode();
            if(messageSecurity!=null){
                if("SignAndEncrypt".equals(messageSecurity)){
                    messageSecurityMode = MessageSecurityMode.SignAndEncrypt;
                    System.out.println("Inside messageSecurity: "+ messageSecurityMode);
                }
                if("Sign".equals(messageSecurity))messageSecurityMode = MessageSecurityMode.Sign;
            }
            // set security policy
            String securityPolicyUri = endpointDescription.getSecurityPolicyUri();
            UserTokenPolicy[] userTokenPolicies = endpointDescription.getUserIdentityTokens();
            if (securityPolicy != null) {
                securityPolicyUri = "http://opcfoundation.org/UA/SecurityPolicy#" + securityPolicy;
                for (int i = 0; i < userTokenPolicies.length; i++) {
                    UserTokenPolicy userTokenPolicy = userTokenPolicies[i];
                    userTokenPolicies[i] = new UserTokenPolicy(userTokenPolicy.getPolicyId(),
                            userTokenPolicy.getTokenType(), userTokenPolicy.getIssuedTokenType(),
                            userTokenPolicy.getIssuerEndpointUrl(), securityPolicyUri);
                }
            }

            // recreate EndpointDescription as returned EndpointDescription from server might not match the specifications
            EndpointDescription endpointDescriptionModified = new EndpointDescription(url,
                    endpointDescription.getServer(), endpointDescription.getServerCertificate(),
                    messageSecurityMode, securityPolicyUri, userTokenPolicies,
                    endpointDescription.getTransportProfileUri(), endpointDescription.getSecurityLevel());

            // create OpcUaClientConfigBuilder
            OpcUaClientConfigBuilder cfg = new OpcUaClientConfigBuilder();

            // set end point
            cfg.setEndpoint(endpointDescriptionModified);

            // set user name and password
            if (username != null & (certPath == null || keyPath == null)) {
                cfg.setIdentityProvider(new UsernameProvider(username, password));
            }

            // set certificates
            if (certPath != null && keyPath != null) {
                X509IdentityProvider x509IdentityProvider = new X509IdentityProvider(certPath, keyPath);
                X509Certificate cert = x509IdentityProvider.getCertificate();
                KeyPair keyPair = new KeyPair(cert.getPublicKey(), x509IdentityProvider.getPrivateKey());
                if (username != null) {
                    cfg.setCertificate(cert).setKeyPair(keyPair).setIdentityProvider(x509IdentityProvider)
                            .setIdentityProvider(new UsernameProvider(username, password));
                } else {
                    cfg.setCertificate(cert).setKeyPair(keyPair).setIdentityProvider(x509IdentityProvider);
                }
            }

            // set ApplicationUri
            if (applicationUri != null) {
                cfg.setApplicationUri(applicationUri);
            }
            return CompletableFuture.completedFuture(OpcUaClient.create(cfg.build()));
        } catch (final UaException e) {
            return (CompletionStage<OpcUaClient>) e;
        }
    });
}

/**
 * Find best ENDPOINT
 *
 * @param endpoints
 * @return
 */
private static EndpointDescription findBest(final List<EndpointDescription> endpoints) {
    /*
     * We simply assume we have at least one and pick the first one. In a more
     * productive scenario you would actually evaluate things like ciphers and
     * security.
     */
    return endpoints.get(0);
}


public void open(OpcuaConnectorEntity opcuaConnectorEntity, String certPath, String keyPath) {
    LOGGER.info("Open connection");
    try {
        opcuaHandler.connect(opcuaConnectorEntity, certPath, keyPath);
    } catch (Exception e) {
        throw new OpcuaException("Failed to connect to OPCUA server \n" + e);
    }
}

public void close() {
    LOGGER.info("Close connection");
    try {
        opcuaHandler.disconnect();
        LOGGER.info("client " + opcuaHandler.getClient());
        Stack.releaseSharedResources();
        Thread.sleep(60000);


    } catch (Exception e) {
        throw new OpcuaException("Failed to close connection \n" + e);
    }
}

public boolean isConnected() {
    try {
        // check client connection
        CompletableFuture<List<DataValue>> future = opcuaHandler.getClient().read(0, TimestampsToReturn.Both,
                asList(Identifiers.RootFolder), asList(AttributeId.DisplayName.uid()));
        List<DataValue> val = future.get();

        // return
        return true;
    } catch (Exception e) {
        LOGGER.info("OPCUA server is not connected!");
    }
    return false;
}

[sc-sityad]

client.disconnect() will solve the problem. Earlier return CompletableFuture.completedFuture(OpcUaClient.create(cfg.build()));
this line cause error if some info is wrong in config builder like certs. So till now I haven't assign the client yet. It shows client has no value and the loop continues infinitly. to solve this I have assign the global variable. like OpcUaClient client = OpcUaClient.create(cfg.build()); opcuaHandler.setClient(client); return CompletableFuture.completedFuture(client);