lmxopcua/tools/opcuacli-dotnet/Commands/SubscribeCommand.cs

using CliFx;
using CliFx.Attributes;
using CliFx.Infrastructure;
using Opc.Ua;
using Opc.Ua.Client;

namespace OpcUaCli.Commands;

[Command("subscribe", Description = "Monitor a node for value changes")]
public class SubscribeCommand : ICommand
{
    /// <summary>
    /// Gets the OPC UA endpoint URL to connect to before subscribing.
    /// </summary>
    [CommandOption("url", 'u', Description = "OPC UA server endpoint URL", IsRequired = true)]
    public string Url { get; init; } = default!;

    [CommandOption("username", 'U', Description = "Username for authentication")]
    public string? Username { get; init; }

    [CommandOption("password", 'P', Description = "Password for authentication")]
    public string? Password { get; init; }

    [CommandOption("security", 'S', Description = "Transport security: none, sign, encrypt (default: none)")]
    public string Security { get; init; } = "none";

    /// <summary>
    /// Gets the node identifier to monitor for value changes.
    /// </summary>
    [CommandOption("node", 'n', Description = "Node ID to monitor", IsRequired = true)]
    public string NodeId { get; init; } = default!;

    /// <summary>
    /// Gets the sampling and publishing interval, in milliseconds, for the monitored item.
    /// </summary>
    [CommandOption("interval", 'i', Description = "Polling interval in milliseconds")]
    public int Interval { get; init; } = 1000;

    /// <summary>
    /// Connects to the OPC UA endpoint and streams monitored-item notifications until cancellation.
    /// </summary>
    /// <param name="console">The console used to display subscription updates.</param>
    public async ValueTask ExecuteAsync(IConsole console)
    {
        using var session = await OpcUaHelper.ConnectAsync(Url, Username, Password, Security);

        var subscription = new Subscription(session.DefaultSubscription)
        {
            PublishingInterval = Interval,
            DisplayName = "CLI Subscription"
        };

        var item = new MonitoredItem(subscription.DefaultItem)
        {
            StartNodeId = new NodeId(NodeId),
            DisplayName = NodeId,
            SamplingInterval = Interval
        };

        item.Notification += (monitoredItem, e) =>
        {
            if (e.NotificationValue is MonitoredItemNotification notification)
            {
                Console.WriteLine(
                    $"[{notification.Value.SourceTimestamp:O}] {NodeId} = {notification.Value.Value} ({notification.Value.StatusCode})");
            }
        };

        subscription.AddItem(item);
        session.AddSubscription(subscription);
        await subscription.CreateAsync();

        await console.Output.WriteLineAsync(
            $"Subscribed to {NodeId} (interval: {Interval}ms). Press Ctrl+C to stop.");

        var ct = console.RegisterCancellationHandler();

        int tick = 0;
        while (!ct.IsCancellationRequested)
        {
            await Task.Delay(2000, ct).ContinueWith(_ => { });
            tick++;
            Console.WriteLine(
                $"  [tick {tick}] Session={session.Connected}, Sub.Id={subscription.Id}, " +
                $"PublishingEnabled={subscription.PublishingEnabled}, " +
                $"MonitoredItemCount={subscription.MonitoredItemCount}, " +
                $"ItemStatus={item.Status?.Id}, " +
                $"LastNotification={((item.LastValue as MonitoredItemNotification)?.Value?.Value)} ({((item.LastValue as MonitoredItemNotification)?.Value?.StatusCode)})");
        }

        await console.Output.WriteLineAsync("Unsubscribed.");
    }
}