 <p>I have solved the problem. It turned out I had to add one line in my NotificationHub class:</p> <pre><code>[HubName("notificationHub")] </code></pre> <p>Now it looks following and this solved my problem.</p> <pre><code>[HubName("notificationHub")] public class NotificationHub : Hub { //public void Hello() //{ // Clients.All.hello(); //} } </code></pre>