SignalR 500 errors during “ping” on Azure website

I've got an ASP.NET 4.5 web app using SignalR 1.0.0-rc1 which I've pushed out to an Azure website for some quick-and-dirty testing (I'm mostly interested in this page here: http://alantaappbeta.azurewebsites.net/api/v3.0/Tests/Sample.htm).

The problem is that the page doesn't seem to want to talk to the SignalR service. The hubs and everything are registered correctly, as http://alantaappbeta.azurewebsites.net/signalr/hubs returns the correct client-side hubs file, and the call to /signalr/negotiate returns some reasonable looking JSON.

{
  "Url":"/signalr",
  "ConnectionId":"a15023f9-c675-4fc2-9fd6-403a297f10c0",
  "KeepAlive":15.0,
  "DisconnectTimeout":40.0,
  "TryWebSockets":false,
  "WebSocketServerUrl":null,
  "ProtocolVersion":"1.1"
}

But when it calls /signalr/ping, it returns a 500 error, with the message "Protocol error: Unknown transport". The stack trace returned in the error page looks like this:

[InvalidOperationException]: Protocol error: Unknown transport.
at Microsoft.AspNet.SignalR.PersistentConnection.ProcessRequestAsync(HostContext context)
at Microsoft.AspNet.SignalR.Hubs.HubDispatcher.ProcessRequestAsync(HostContext context)
at Microsoft.AspNet.SignalR.Owin.CallHandler.Invoke(IDictionary`2 environment)
at Microsoft.AspNet.SignalR.Owin.Handlers.HubDispatcherHandler.Invoke(IDictionary`2 environment)
at Microsoft.Owin.Host.SystemWeb.OwinCallContext.Execute()
at Microsoft.Owin.Host.SystemWeb.OwinHttpHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object extraData)
at Microsoft.Owin.Host.SystemWeb.OwinHttpHandler.System.Web.IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, Object extraData)
at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

Because this is on Azure, I don't have access to all the troubleshooting tools you'd normally have, but what logs I have been able to get access to don't give me any information beyond the above.

I suppose it goes without saying that this runs fine on my local IIS instance :-).

Any suggestions?

Edit: This is how I'm opening my connection:

$.connection.hub.start({
    transport: 'auto',
    xdomain: true
}).done(function () {
    console.log('Connected with hub.id=' + $.connection.hub.id);
}).fail(function (e) {
    console.log('Unable to connect to SignalR Hubs: ' + e);
});

But neither the .done() nor the .fail() handlers are being called.

Oddly enough, if I set the transport to 'longPolling', I can get it to fail in a similar manner using IIS Express on my local box. But it doesn't seem to make any difference what I set the transport to on Azure: I still get the same error.

It turns out that the issue was that I had a mix of different versions of SignalR on my machine: I was using the server-side DLLs from the NuGet package (1.0.0-rc1), but the JavaScript client file was from the dev branch. Once I got them all synchronized, everything worked. I'm still not sure precisely why the issue only showed up with Azure, but I suspect it has something to do with the precise transports supported by the different versions of IIS.