获取连接到SignalR集线器的侦听器,客户端的数量

Question

有没有办法找出侦听器的数量(连接到集线器的客户端？)

如果至少连接了一个客户端,我正在尝试运行/启动任务,否则不启动它:

[HubName("taskActionStatus")]
public class TaskActionStatus : Hub, IDisconnect
{
    static CancellationTokenSource tokenSource;

    public void GetTasksStatus(int? siteId)
    {
        tokenSource = new CancellationTokenSource();
        CancellationToken ct = tokenSource.Token;

        ITaskRepository taskRepository = UnityContainerSetup.Container.Resolve<ITaskRepository>();

        // init task for checking task statuses
        var tasksItem = new DownloadTaskItem();
        taskRepository.GetTasksStatusAsync(siteId, tasksItem, ct);

        // subscribe to event [ listener ]
        tasksItem.Changed += new EventHandler<TaskEventArgs>(UpdateTasksStatus);
    }

    public void UpdateTasksStatus(object sender, TaskEventArgs e)
    {
        Clients.updateMessages(e.Tasks);
    }

    // when browsing away from page
    public Task Disconnect()
    {
        try
        {
            tokenSource.Cancel();
        }
        catch (Exception)
        {
            //
        }

        return null;
    }
}

谢谢

Answer 1

没有办法从SignalR那里得到这个数.您必须使用Hub上的OnConnect()和OnDisconnect()方法来自行计算.

使用静态类来保存计数的简单示例:

public static class UserHandler
{
    public static HashSet<string> ConnectedIds = new HashSet<string>();
}

public class MyHub : Hub
{
    public override Task OnConnected()
    {
        UserHandler.ConnectedIds.Add(Context.ConnectionId);
        return base.OnConnected();
    }

    public override Task OnDisconnected()
    {
        UserHandler.ConnectedIds.Remove(Context.ConnectionId);
        return base.OnDisconnected();
    }
}

然后你从中获得计数UserHandler.ConnectedIds.Count.

Answer 2

对于版本2.1.1+,它应该是:

public static class UserHandler
{
    public static HashSet<string> ConnectedIds = new HashSet<string>();
}

public class MyHub : Hub
{
    public override Task OnConnected()
    {
        UserHandler.ConnectedIds.Add(Context.ConnectionId);
        return base.OnConnected();
    }

    public override Task OnDisconnected(bool stopCalled)
    {
        UserHandler.ConnectedIds.Remove(Context.ConnectionId);
        return base.OnDisconnected(stopCalled);
    }
}

Answer 3

在 SIGnalR（2.4.1 版）中，这很容易：

public int GetOnline()
{
   return GlobalHost.DependencyResolver.Resolve<ITransportHeartbeat>().GetConnections().Count;
}

只需从客户端调用此方法（：

Answer 4

现在您需要：

public override Task OnConnectedAsync()
    {
        UserHandler.ConnectedIds.Add(Context.ConnectionId);

        return base.OnConnectedAsync();
    }

    public override Task OnDisconnectedAsync(Exception exception)
    {
        UserHandler.ConnectedIds.Remove(Context.ConnectionId);
        return base.OnDisconnectedAsync(exception);
    }