// @nuget: Workstation.UaClient -version 2.4.0

using System;

using System.Linq;

using System.Reactive.Linq;

using System.Threading.Tasks;

using Workstation.ServiceModel.Ua;

using Workstation.ServiceModel.Ua.Channels;

public class Program

{

    /// <summary>

    /// Creates a data subscription and monitors the current time.

    /// </summary>

    public static async Task Main()

    {

        // describe this client application.

        var clientDescription = new ApplicationDescription

        {

            ApplicationName = "Workstation.UaClient.FeatureTests",

            ApplicationUri = $"urn:{System.Net.Dns.GetHostName()}:Workstation.UaClient.FeatureTests",

            ApplicationType = ApplicationType.Client

        };

​

        // create a 'UaTcpSessionChannel', a client-side channel that opens a 'session' with the server.

        var channel = new UaTcpSessionChannel(

            clientDescription,

            null, // no x509 certificates

            new AnonymousIdentity(), // no user identity

            "opc.tcp://opcua.rocks:4840", // the public endpoint of a server at opcua.rocks.

            SecurityPolicyUris.None); // no encryption

        try

        {

            // try opening a session and reading a few nodes.

            await channel.OpenAsync();

​

            Console.WriteLine($"Opened session with endpoint '{channel.RemoteEndpoint.EndpointUrl}'.");

            Console.WriteLine($"SecurityPolicy: '{channel.RemoteEndpoint.SecurityPolicyUri}'.");

            Console.WriteLine($"SecurityMode: '{channel.RemoteEndpoint.SecurityMode}'.");

            Console.WriteLine($"UserIdentityToken: '{channel.UserIdentity}'.");

​

            // build a CreateSubscriptionRequest. See 'OPC UA Spec Part 4' paragraph 5.13.2

            var req = new CreateSubscriptionRequest

            {

                RequestedPublishingInterval = 1000.0, // intervals are in milliseconds

                RequestedMaxKeepAliveCount = 30,

                RequestedLifetimeCount = 30 * 3,

                PublishingEnabled = true,

            };

            var res = await channel.CreateSubscriptionAsync(req);

​

            // the result will return the server's subscription id. You will needs this to 

            // add monitored items.

            var id = res.SubscriptionId;

            Console.WriteLine($"Created subscription '{id}'.");

​

            // build a CreateMonitoredItemsRequest. See 'OPC UA Spec Part 4' paragraph 5.12.2

            var req2 = new CreateMonitoredItemsRequest

            {

                SubscriptionId = id,

                TimestampsToReturn = TimestampsToReturn.Both,

                ItemsToCreate = new MonitoredItemCreateRequest[]

                {

                    new MonitoredItemCreateRequest

                    {

                        ItemToMonitor= new ReadValueId{ AttributeId= AttributeIds.Value, NodeId= NodeId.Parse(VariableIds.Server_ServerStatus_CurrentTime)},

                        MonitoringMode= MonitoringMode.Reporting,

                        // specify a unique ClientHandle. The ClientHandle is returned in the PublishResponse

                        RequestedParameters= new MonitoringParameters{ ClientHandle= 42, QueueSize= 2, DiscardOldest= true, SamplingInterval= 1000.0},

                    },

                },

            };

            var res2 = await channel.CreateMonitoredItemsAsync(req2);

​

            Console.WriteLine("Subscribe to PublishResponse stream for 5s.");

            // when the session is open, the client sends a stream of PublishRequests to the server.

            // You can subscribe to all the PublishResponses -or- subscribe to the responses from 

            // a single subscription.

            var token = channel

                // receive just the subscription we just created

                .Where(pr => pr.SubscriptionId == id)

                // subscribe with an 'OnNext' function, and an 'OnError' function

                .Subscribe(

                    pr =>

                    {

                        // loop thru all the data change notifications

                        var dcns = pr.NotificationMessage.NotificationData.OfType<DataChangeNotification>();

                        foreach (var dcn in dcns)

                        {

                            foreach (var min in dcn.MonitoredItems)

                            {

                                Console.WriteLine($"sub: {pr.SubscriptionId}; handle: {min.ClientHandle}; value: {min.Value}");

                            }

                        }

                    },

                    ex => Console.WriteLine("Exception in publish response handler: {0}", ex.GetBaseException().Message)

            );

​

            // publish for 5 seconds and then close.

            await Task.Delay(5000);

            Console.WriteLine($"\nClosing session '{channel.SessionId}'.");

            await channel.CloseAsync();

        }

        catch(Exception ex)

        {

            await channel.AbortAsync();

            Console.WriteLine(ex.Message);

        }

    }

}