SignalR CORS error on request for Hub method

I am just trying to configure SignalR to run owin and I want to connect via a JavaScript client. Should be easy? I was able to quickly set up the SignalR server and connect to the server. However, when the called callback is called on the client, I try to make a call to the dispatch method of the hubs and I get the following error in the console:

XMLHttpRequest cannot load http: // localhost: 8199 / signalr / signalr / send? Transport = serverSentEvents & clien ... AxBg6iaFwlK50s2DnurE & connectionData =% 5B% 7B% 22name% 22% 3A% 22testhub% 22% 7D% 5D. The requested resource does not have an "Access-Control-Allow-Origin" header. Origin ' http: // localhost ' is therefore not allowed. The response was HTTP status code 500.

Here is my server-side code:

    public static IAppBuilder UseService(this IAppBuilder app)
    {
        log4net.Config.XmlConfigurator.Configure();
        app.UseService(NinjectConfig.CreateKernel);
        app.UseLogging();
        app.UseSignalr();
        return app;
    }

      

        
        
        
      

    

    internal static IAppBuilder UseSignalr(this IAppBuilder app)
    {
        app.Map("/signalr", map =>
            {
               map.UseCors(CorsOptions.AllowAll);

                var hubConfig = new HubConfiguration {EnableDetailedErrors = true};
                map.RunSignalR(hubConfig);
            }
        );
        return app;
    }

      

        
        
        
      

    

Here is the client side:

    var connection = $.hubConnection('http://localhost:8199/signalr');
    var testHub = connection.createHubProxy('testHub');

    testHub.on('addMessage', function(name){
        console.log(name);
    });

    connection.start().done(function () {
            testHub.invoke('send', 'testName');
        }).fail(function (e) {
            console.log('Failed to connect');
        });
        connection.error(function(error){
        console.log(error);
    });

      

        
        
        
      

    

Why does a CORS request work for a startup call rather than a subsequent call to a hub method?

Update: In the network tab, I see there is a call: http: // localhost8199 / signalr / negotiate - this call works and CORS headers will return a response as expected

Then: http: // localhost: 8199 / signalr / connect is called and this call also has the correct CORS headers and works.

Then the call comes up: http: // localhost: 8199 / signalr / start Here the same good things happen.

Finally, there is a call: http: // localhost: 8199 / signalr / send and this is a called call and there are null CORS headers in the error message.

Update:

I also tried to configure my client like this:

    $.connection.hub.url = 'http://localhost:8199/signalr';
        var proxy = $.connection.testHub;
        proxy.client.addMessage = function(name){
            console.log(name);
    };

    $.connection.hub.start()
    .done(function () {
        console.log($.connection.hub.id);
        proxy.server.sendMessage()
            .done(function(val){
                console.log(val);
            });
     })
    .fail(function (e) {
        console.log('Failed to connect');
    });

      

        
        
        
      

    

I have little hope for this to work as I feel the problem is with the server. But just wanted to clarify what I've tried here.