You can use the IAppBuilder.UseErrorPage() extension method to see exception details instead of a blank 500 response. This method is available via the Microsoft.Owin.Diagnostics NuGet package.
Make sure you call UseErrorPage
before calling MapSignalR
or adding other middleware that may throw an exception.
More information on UseErrorPage
can be found in the Add OWIN Diagnostics section of the following article: http://www.asp.net/aspnet/overview/owin-and-katana/getting-started-with-owin-and-katana