SignalR - Server side method to detect if a client disconnects from a hub?

Question

I'm wanting to stop a System.Timers.Timer that is running in a SignalR hub after a client closes a window/tab containing the active connection.

I have tried sending a bool value to the server by calling server code to notify the server the client is still connected or not, but it's not currently working.

window.onbeforeunload = function () {
    profile.server.setIsConnected(false);
};

Server Side:

public ProfileHub()
{  
    timer = new Timer(15000);
    timer.Elapsed += (sender, e) => { timer_Elapsed(sender, e, _isActive); };
    timer.AutoReset = false;
}

[Authorize]
private void timer_Elapsed(object sender, ElapsedEventArgs e, bool active)
{            
    timer.Stop();

    if (active)
    {
        System.Diagnostics.Debug.WriteLine("Timer Started");
        timer.Start();
    }
    else
    {
        System.Diagnostics.Debug.WriteLine("Timer Stopped");
        return;
    }
    // process code
}

[Authorize]
public void SetIsActive(bool isActive)
{
    _isActive = isActive;
}

Is this possible and am I on the right track? I suspect it has something to do with the anonymous delegate for timer.Elapsed, but I'm not entirely sure.

Minter

Got solution for this ? – Aquacade

Answer 1

SignalR has OnConnected, OnDisconnected, and OnReconnected that are called every time the client does one of those actions. You can simply override them:

public override Task OnConnected()
{
    return base.OnConnected();
}

public override Task OnDisconnected()
{
    //custom logic here
    return base.OnDisconnected();
}

public override Task OnReconnected()
{
    return base.OnReconnected();
}

I've found them to be extremely useful also for debugging purposes. If you're wanting to set a timer for each person, you should use some sort of connectionMapping along with the above functions to keep track of your users.

Amorino

Thanks for the quick response! This is just what I needed. I will look at connection mapping to keep track of each timer. – Minter

Sure thing. I use a slightly modified version of the In-Memory Storage code presented here and it works great – Amorino

Answer 2

You should use the method OnDisconnected instead of the timer. Here's the official documentation, but the framework gives you events when a connected client disconnects or reconnects.

Bodi

OnDisconnected does not always fire though – Diadiabase

But on all his scenarios: "The OnDisconnected method doesn't get called in some scenarios, such as when a server goes down or the App Domain gets recycled." So id DOES always fire if the Client is the reason for disconnecting. – Raffinose