title: SignalR "Start must be called before data can be sent" when responding to a server request
body: <p>I have some SignalR client code that invokes a server method after a request from the server:</p>
  
  <pre><code>        var connection = new HubConnection(_hubAddress);
          var hubProxy = _hubConnection.CreateHubProxy(HubName);
          connection.Start().Wait(TimeSpan.FromMinutes(1));
    ...
  
          hubProxy.On("Client_Method", (string callerId, string requestIdentifier) =&gt;
          {
             if (connection.State == ConnectionState.Connected)
             {
                // error hapening on the invoke call here, despite 
                // the connection state being connected.  
                // Do I need to call Start here?
                hubProxy.Invoke("Proxy_Method_Callback", callerId, requestIdentifier);
             }
          });
  </code></pre>
  
  <p>But its throwing an exception: </p>
  
  <blockquote>
    <p>InvalidOperationException: Data cannot be sent because the connection
    is in the disconnected state. Call start before sending any data.</p>
  </blockquote>
  
  <p>But if the hubProxy is connected and open to receive the request, why is it erroring on the invoke?</p>