Intermittent SignalR 404s

Question

User1486521414 posted

I'm having problems with calls to /signalr/start returning a 404 response intermittently. I will get this about 5 out of every 10 page loads when using Chrome. I do not see the issue in IE11 or Edge.

I noticed initially that serverSentEvents was being used, even though that was not the primary transport option. As a result, I enabled web sockets on IIS, and now I will also sometimes see 404s when calling /signalr/connect intermittently from Chrome.

I am running SignalR version 2.4.1, which I understand is the most recent version. I'm running Chrome 86.0.4240.193. The IIS version is 10.

I read a StackOverflow article that mentioned allowing for very long URLs via the web.config. I tried that and it did not help.

Does anyone have any additional troubleshooting recommendations?

Answer 1

User475983607 posted

What is the URL that causes the 404?  Typically SignalR is single page application.  Are you doing an HTTP get to another page?  

Answer 2

User1486521414 posted

When I load my web page, it initiates a get to https://www.mydomain.com/signalr/start?transport=serverSentEvents... This is where I see intermittent 404s in Chrome. I don't believe this would be considered a get to another page, but I also admit that I am a SignalR novice.

Answer 3

User1486521414 posted

I discovered the solution. Our site was supposed to be using windows authentication at the top level, but had both anonymous and windows authentication enabled. I disabled anonymous authentication at the top level and the issue went away.