SignalR - Checking if a user is still connected
From http://forums.asp.net/t/1829432.aspx/1?How+do+I+get+list+of+connected+clients+on+signalr+
IHubContext context = GlobalHost.ConnectionManager.GetHubContext<MyHub>();
context.Clients.notify("Hello world");
So you should be able to get context.Clients.Count.
That post also references the wiki which has lots of good info. You could try using the OnConnected/OnDisconnected examples to track the users, and when you get to zero users stop your call.
Probably the most used solution is to keep a static variable containing users currently connected and overriding OnConnect
and OnDisconnect
or implementing IDisconnect
depending on the version that you use.
You would implement something like this:
public class MyHub : Hub
{
private static List<string> users = new List<string>();
public override Task OnConnected()
{
users.Add(Context.ConnectionId);
return base.OnConnected();
}
//SignalR Verions 1 Signature
public override Task OnDisconnected()
{
users.Remove(Context.ConnectionId);
return base.OnDisconnected();
}
//SignalR Version 2 Signature
public override Task OnDisconnected(bool stopCalled)
{
users.Remove(Context.ConnectionId);
return base.OnDisconnected(stopCalled);
}
// In your delegate check the count of users in your list.
}
If you save your connectionId in your database, you can check this:
var heartBeat = GlobalHost.DependencyResolver.Resolve<ITransportHeartbeat>();
var connectionAlive = heartBeat.GetConnections().FirstOrDefault(c=>c.ConnectionId == connection.ConnectionId);
if (connectionAlive.IsAlive)
{
//Do whatever...
}
I have done this way:
public class PrincipalCommunicator
{
public readonly static Lazy<PrincipalCommunicator> _instance = new Lazy<PrincipalCommunicator>(
() => new PrincipalCommunicator(GlobalHost.ConnectionManager.GetHubContext<PrincipalHub>())
);
public List<string> ConnectedUsers { get; set; }
private IHubContext _context;
private PrincipalCommunicator(IHubContext context)
{
ConnectedUsers = new List<string>();
_context = context;
}
public static PrincipalCommunicatorInstance
{
get
{
return _instance.Value;
}
}
public bool IsUserConnected(string user)
{
return UsuariosConectados.Contains(user);
}
}
public class PrincipalHub : Hub
{
public override Task OnConnected()
{
PrincipalComunicador.Instance.UsuariosConectados.Add(Context.User.Identity.Name);
return base.OnConnected();
}
public override Task OnDisconnected(bool stopCalled)
{
PrincipalComunicador.Instance.UsuariosConectados.Remove(Context.User.Identity.Name);
return base.OnDisconnected(stopCalled);
}
}
}
This way, all logic to send something to client stays in one place, like the example and you can know if a user is connected anywhere in the code.