OPC Client for milo fails to connect to local OPC discovery service

Question

I am new to OPC UA and I am using milo OPC Subscriber client to connect to local discovery service. I have Prosys simulation server which is connected to my local discovery service.

Note: If I connect directly to prosys endpoint it works fine. It fails only through discovery service.

I get the following exception when I run my code

<pre>12:38:35.916 [main] INFO org.eclipse.milo.opcua.stack.core.Stack -
Successfully removed cryptography restrictions. 12:38:36.167 [main]
INFO com.company.OpcuaClientRunner - security temp dir:
C:\Users\Z003Z2YP\AppData\Local\Temp\security 12:38:36.173 [main] INFO
com.company.KeyStoreLoader - Loading KeyStore at
C:\Users\Z003Z2YP\AppData\Local\Temp\security\example-client.pfx
12:38:37.594 [main] INFO com.company.OpcuaClientRunner - Using
endpoint: opc.tcp://<hostname>:4840 [None] 12:38:37.600 [main] INFO
org.eclipse.milo.opcua.sdk.client.OpcUaClient - Eclipse Milo OPC UA
Stack version: 0.2.3 12:38:37.600 [main] INFO
org.eclipse.milo.opcua.sdk.client.OpcUaClient - Eclipse Milo OPC UA
Client SDK version: 0.2.3 12:38:37.809 [NonceUtilSecureRandom] INFO
org.eclipse.milo.opcua.stack.core.util.NonceUtil - SecureRandom seeded
in 0ms. 12:38:37.815 [ua-netty-event-loop-1] ERROR
org.eclipse.milo.opcua.stack.client.handlers.UaTcpClientMessageHandler
- [remote=<hostname>/<IP>:4840] errorMessage=ErrorMessage{error=StatusCode{name=Bad_ServiceUnsupported,
value=0x800B0000, quality=bad}, reason=null} 12:38:53.828 [main] ERROR
com.company.OpcuaClientRunner - Error running client example:
UaException: status=Bad_Timeout, message=request timed out after
16000ms java.util.concurrent.ExecutionException: UaException:
status=Bad_Timeout, message=request timed out after 16000ms     
at java.util.concurrent.CompletableFuture.reportGet(CompletableFuture.java:357)
at java.util.concurrent.CompletableFuture.get(CompletableFuture.java:1895)
at com.company.OpcuaSubscriber.run(OpcuaSubscriber.java:49)     
at com.company.OpcuaClientRunner.run(OpcuaClientRunner.java:122)    
at com.company.OpcuaSubscriber.main(OpcuaSubscriber.java:120) Caused by:
org.eclipse.milo.opcua.stack.core.UaException: request timed out after
16000ms     
at org.eclipse.milo.opcua.stack.client.UaTcpStackClient.lambda$scheduleRequestTimeout$13(UaTcpStackClient.java:326)
at io.netty.util.HashedWheelTimer$HashedWheelTimeout.expire(HashedWheelTimer.java:581)
at io.netty.util.HashedWheelTimer$HashedWheelBucket.expireTimeouts(HashedWheelTimer.java:655)
at io.netty.util.HashedWheelTimer$Worker.run(HashedWheelTimer.java:367)
at java.lang.Thread.run(Thread.java:748) 12:38:53.828 [main] ERROR
com.company.OpcuaClientRunner - Error running example: UaException:
status=Bad_Timeout, message=request timed out after 16000ms
java.util.concurrent.ExecutionException: UaException:
status=Bad_Timeout, message=request timed out after 16000ms     
at java.util.concurrent.CompletableFuture.reportGet(CompletableFuture.java:357)
at java.util.concurrent.CompletableFuture.get(CompletableFuture.java:1895)
at com.company.OpcuaSubscriber.run(OpcuaSubscriber.java:49)     
at com.company.OpcuaClientRunner.run(OpcuaClientRunner.java:122)    
at com.company.OpcuaSubscriber.main(OpcuaSubscriber.java:120) Caused by:
org.eclipse.milo.opcua.stack.core.UaException: request timed out after
16000ms     
at org.eclipse.milo.opcua.stack.client.UaTcpStackClient.lambda$scheduleRequestTimeout$13(UaTcpStackClient.java:326)
at io.netty.util.HashedWheelTimer$HashedWheelTimeout.expire(HashedWheelTimer.java:581)
at io.netty.util.HashedWheelTimer$HashedWheelBucket.expireTimeouts(HashedWheelTimer.java:655)
at io.netty.util.HashedWheelTimer$Worker.run(HashedWheelTimer.java:367)
at java.lang.Thread.run(Thread.java:748)</pre>

Code to create client in ClientRunner.

private OpcUaClient createClient() throws Exception {
        File securityTempDir = new File(System.getProperty("java.io.tmpdir"), "security");
        if (!securityTempDir.exists() && !securityTempDir.mkdirs()) {
            throw new Exception("unable to create security dir: " + securityTempDir);
        }
        LoggerFactory.getLogger(getClass())
            .info("security temp dir: {}", securityTempDir.getAbsolutePath());

        KeyStoreLoader loader = new KeyStoreLoader().load(securityTempDir);
        loader.load();

        SecurityPolicy securityPolicy = client.getSecurityPolicy();
        EndpointDescription[] endpoints;

        try {
            endpoints = UaTcpStackClient
                .getEndpoints(client.getEndpointUrl())
                .get();
        } catch (Throwable ex) {
            ex.printStackTrace();
            // try the explicit discovery endpoint as well
            String discoveryUrl = client.getEndpointUrl();
            logger.info("Trying explicit discovery URL: {}", discoveryUrl);
            endpoints = UaTcpStackClient
                .getEndpoints(discoveryUrl)
                .get();
        }

        EndpointDescription endpoint = Arrays.stream(endpoints)
            .filter(e -> e.getSecurityPolicyUri().equals(securityPolicy.getSecurityPolicyUri()))
            .findFirst().orElseThrow(() -> new Exception("no desired endpoints returned"));
        logger.info("Using endpoint: {} [{}]", endpoint.getEndpointUrl(), securityPolicy);

        OpcUaClientConfig config = OpcUaClientConfig.builder()
            .setApplicationName(LocalizedText.english("eclipse milo opc-ua client"))
            .setApplicationUri("urn:eclipse:milo:examples:client")
            .setCertificate(loader.getClientCertificate())
            .setKeyPair(loader.getClientKeyPair())
            .setEndpoint(endpoint)
            .setIdentityProvider(client.getIdentityProvider())
            .setRequestTimeout(uint(5000))
            .build();

        return new OpcUaClient(config);

Client interface class

public interface OpcuaClientInterface {

        public static final String USERNAME = "demo";
        public static final String PASSWORD = "demo";

        default String getEndpointUrl() {
            return "opc.tcp://localhost:4840/UADiscovery";
        }

        default SecurityPolicy getSecurityPolicy() {
             return SecurityPolicy.None;
        }


        default IdentityProvider getIdentityProvider() {
    //       return new UsernameProvider(USERNAME,PASSWORD);
            return new AnonymousProvider();
        }

        void run (OpcUaClient client, CompletableFuture future) throws Exception;

    }

subscriber run implementation

    @Override
    public void run(OpcUaClient client, CompletableFuture future) throws Exception {
        // synchronous connect
        client.connect().get();

        // create a subscription @ 1000ms
        UaSubscription subscription = client.getSubscriptionManager().createSubscription(1000.0).get();

        List nodeIds = Arrays.asList("SuctionPressure", "DischargePressure", "Flow", "BearingTemperature", "Vibration", "Power");
//      List nodeIds = Arrays.asList("DS", "PV");

        List MICRs = nodeIds.stream().map(id -> {
            ReadValueId readValueId = new ReadValueId(new NodeId(3, id), AttributeId.Value.uid(), null,
                    QualifiedName.NULL_VALUE);

            // important: client handle must be unique per item
            UInteger clientHandle = uint(clientHandles.getAndIncrement());

            MonitoringParameters parameters = new MonitoringParameters(clientHandle, 1000.0, // sampling interval
                    null, // filter, null means use default
                    uint(10), // queue size
                    true // discard oldest
            );

            MonitoredItemCreateRequest request = new MonitoredItemCreateRequest(readValueId, MonitoringMode.Reporting,
                    parameters);
            return request;
        }).collect(Collectors.toList());

        // when creating items in MonitoringMode.Reporting this callback is where each
        // item needs to have its
        // value/event consumer hooked up. The alternative is to create the item in
        // sampling mode, hook up the
        // consumer after the creation call completes, and then change the mode for all
        // items to reporting.
        BiConsumer onItemCreated = (item, id) -> item
                .setValueConsumer(this::onSubscriptionValue);

        List items = subscription.createMonitoredItems(TimestampsToReturn.Both, MICRs, onItemCreated)
                .get();

        for (UaMonitoredItem item : items) {
            if (item.getStatusCode().isGood()) {
                logger.info("item created for nodeId={}", item.getReadValueId().getNodeId());
            } else {
                logger.warn("failed to create item for nodeId={} (status={})", item.getReadValueId().getNodeId(),
                        item.getStatusCode());
            }
        }

        // let the example run for 5 seconds then terminate
        // Thread.sleep(1000 * 60 * 1);
        // future.complete(client);
    }

Answer 1

I think you may be confused about what a Discovery Server does.

You don't connect "through" a Discovery Server to another server. It's more like a registry where other servers can register themselves and then clients can go and see what servers are available.

The client queries the discovery server for a list of servers, selects one, and then connects directly to that server using the information obtained from the discovery server.

Answer 2

I got it working with the milo OPC Subscriber client.

following is the changes I did in the classes.

Client Interface

public interface OpcuaClientInterface {

public static final String USERNAME = "demo";
public static final String PASSWORD = "demo";
public static final String UaServerName = "SimulationServer";

default String getEndpointUrl() {
    return "opc.tcp://localhost:4840";
}

default SecurityPolicy getSecurityPolicy() {
     return SecurityPolicy.None;
}

default String getUaServerName () {
    return UaServerName;
}


default IdentityProvider getIdentityProvider() {
     return new UsernameProvider(USERNAME,PASSWORD);
}

void run (OpcUaClient client, CompletableFuture<OpcUaClient> future) throws Exception;

}

client runner class

public class OpcuaClientRunner {

static {
    CryptoRestrictions.remove();
    Security.addProvider(new BouncyCastleProvider());
}
private final AtomicLong requestHandle = new AtomicLong(1L);

private final Logger logger = LoggerFactory.getLogger(getClass());
private final CompletableFuture<OpcUaClient> future = new CompletableFuture<>();

private final OpcuaClientInterface client;

public OpcuaClientRunner(OpcuaClientInterface client) throws Exception {
    this.client = client;
}

private KeyStoreLoader createKeyStore() {
    KeyStoreLoader loader = null;
    try {
        File securityTempDir = new File(System.getProperty("java.io.tmpdir"), "security");
        if (!securityTempDir.exists() && !securityTempDir.mkdirs()) {
            throw new Exception("unable to create security dir: " + securityTempDir);
        }
        LoggerFactory.getLogger(getClass()).info("security temp dir: {}", securityTempDir.getAbsolutePath());
        loader = new KeyStoreLoader().load(securityTempDir);
        loader.load();
    } catch (Exception e) {
        logger.error("Could not load keys {}", e);
        return null;
    }
    return loader;
}

private CompletableFuture<ServerOnNetwork[]> findServersOnNetwork(String discoveryEndpointUrl)
        throws InterruptedException, ExecutionException {
    UaStackClient c = createDiscoveryClient(client.getEndpointUrl()).connect().get();
    RequestHeader header = new RequestHeader(NodeId.NULL_VALUE, DateTime.now(),
            uint(requestHandle.getAndIncrement()), uint(0), null, uint(60), null);

    FindServersOnNetworkRequest request = new FindServersOnNetworkRequest(header, null, null, null);

    return c.<FindServersOnNetworkResponse>sendRequest(request).thenCompose(result -> {
        StatusCode statusCode = result.getResponseHeader().getServiceResult();

        if (statusCode.isGood()) {
            return CompletableFuture.completedFuture(result.getServers());
        } else {
            CompletableFuture<ServerOnNetwork[]> f = new CompletableFuture<>();
            f.completeExceptionally(new UaException(statusCode));
            return f;
        }
    });
}

private UaTcpStackClient createDiscoveryClient(String endpointUrl) {
    KeyStoreLoader loader = createKeyStore();
    if (loader == null) {
        return null;
    }
    UaTcpStackClientConfig config = UaTcpStackClientConfig.builder()
            .setApplicationName(LocalizedText.english("Stack Example Client"))
            .setApplicationUri(String.format("urn:example-client:%s", UUID.randomUUID()))
            .setCertificate(loader.getClientCertificate()).setKeyPair(loader.getClientKeyPair())
            .setEndpointUrl(endpointUrl).build();

    return new UaTcpStackClient(config);
}

private OpcUaClient createUaClient() throws Exception {

    KeyStoreLoader loader = createKeyStore();
    if (loader == null) {
        return null;
    }

    SecurityPolicy securityPolicy = client.getSecurityPolicy();
    EndpointDescription[] endpoints = null;

    try {
        ServerOnNetwork[] servers = findServersOnNetwork(client.getEndpointUrl()).get();
        ServerOnNetwork server = Arrays.stream(servers)
                .filter(e -> e.getServerName().equals(client.getUaServerName())).findFirst()
                .orElseThrow(() -> new Exception("no desired UA Server returned."));
        endpoints = UaTcpStackClient.getEndpoints(server.getDiscoveryUrl()).get();
    } catch (Throwable ex) {
        ex.printStackTrace();
    }

    EndpointDescription endpoint = Arrays.stream(endpoints)
            .filter(e -> e.getSecurityPolicyUri().equals(securityPolicy.getSecurityPolicyUri())).findFirst()
            .orElseThrow(() -> new Exception("no desired endpoints returned"));
    logger.info("Using endpoint: {} [{}]", endpoint.getEndpointUrl(), securityPolicy);

    OpcUaClientConfig config = OpcUaClientConfig.builder()
            .setApplicationName(LocalizedText.english("eclipse milo opc-ua client"))
            .setApplicationUri("urn:eclipse:milo:examples:client").setCertificate(loader.getClientCertificate())
            .setKeyPair(loader.getClientKeyPair()).setEndpoint(endpoint)
            .setIdentityProvider(client.getIdentityProvider()).setRequestTimeout(uint(5000)).build();

    return new OpcUaClient(config);
}

public void run() {
    try {
        OpcUaClient uaClient = createUaClient();
        future.whenComplete((c, ex) -> {
            if (ex != null) {
                logger.error("Error running example: {}", ex.getMessage(), ex);
            }

            try {
                uaClient.disconnect().get();
                Stack.releaseSharedResources();
            } catch (InterruptedException | ExecutionException e) {
                logger.error("Error disconnecting:", e.getMessage(), e);
            }

            try {
                Thread.sleep(1000);
                System.exit(0);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        });

        try {
            client.run(uaClient, future);
            future.get(15, TimeUnit.SECONDS);
        } catch (Throwable t) {
            logger.error("Error running client example: {}", t.getMessage(), t);
            future.completeExceptionally(t);
        }

    } catch (Throwable t) {
        logger.error("Error getting client: {}", t.getMessage(), t);

        future.completeExceptionally(t);

        try {
            Thread.sleep(1000);
            System.exit(0);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    /*
     * try { Thread.sleep(999999999); } catch (InterruptedException e) {
     * e.printStackTrace(); }
     */
}

}