SignalR notification from server to client

I want to push a notification from my server to client. I've tried the chat tutorial found here but this just sends chat messages from one client to client

What I want is a button whose onClick method is running at server. Once, I click this button, notifications (a string message) must be sent to all clients.

My Hub class is

 public class NotificationsHub : Hub
{
    public void SendNotification(string author, string message)
    {
        Clients.All.broadcastNotification(author, message);
    }
}

and in the button click, I try this

var context = GlobalHost.ConnectionManager.GetHubContext<NotificationsHub>();
context.Clients.All.SendNotification("Admin", "stop the chat");

But still, I'm not able to notify the clients. Nothing is happening. What am I doing wrong??

My JS at client web page to notify is like this

 <script type="text/javascript">
    $(function () {


        // Declare a proxy to reference the hub. 
        var notifications = $.connection.notificationsHub;
        // Create a function that the hub can call to broadcast messages.
        notifications.client.broadcastNotification = function (name, message) {
            alert(name + " says '" + message + "'");

        };

You need to call broadcastNotification in your button click function, like below:

var context = GlobalHost.ConnectionManager.GetHubContext<NotificationsHub>();
context.Clients.All.broadcastNotification("Admin", "stop the chat");

Also, you need to start the hub by adding $.connection.hub.start(), your JS file should be like:

<script src="~/Scripts/jquery-1.10.2.js"></script>
<script src="~/Scripts/jquery.signalR-2.0.1.js"></script>
<script src="/signalr/hubs"></script>

 <script type="text/javascript">   
  $(function () {
       var notifications = $.connection.notificationsHub;
        notifications.client.broadcastNotification = function (name, message) {
            alert(name + " says '" + message + "'");
        $.connection.hub.start();
   };
</script>