I have an ASP.Net MVC application that I have added SignalR to. After following the "Getting Started" tutorial (with modifications of course since it's going in my application) I got it working on localhost. However once it's in the production environment, I get the following error:
WebSocket connection to 'ws://xxxxx/signalr/connect?transport=webSockets&clientProtocol=1.5&connectionToken=xxxxx' failed: Connection closed before receiving a handshake response.
I can access /signalr/hubs (I get a js file). Any ideas as to why this would happen?
This may be due to the fact that your web server doesn't support WebSockets (IIS 7.5, for instance. It may also be due to the fact that you are using a "proxy" server like ARR and it just cannot "route" WebSocket requests.
The first thing I would try to do is to disable WebSockets on SignalR, just as a debug tool. Here's how: SignalR - How do I disable WebSockets
If your problem persists, it's a general SignalR problem but at least you will have a more specific error. If the problem stops, now you know it is a server issue.
来源：https://stackoverflow.com/questions/31011288/signalr-2-2-0-websocket-error-connecting-to-hub