SignalR: Error during WebSocket handshake: Unexpected response code: 400

Question

I have just started working with SignalR. I have implemented real-time data reflection on my site using signalr. I was getting \"Error during Web-Socket handshake: Unexpecte

Answer 1

This 400 error can also happen if you are running on multiple servers behind a load balancer. Inspect the body of the 400 response (ex., using Fiddler) and see if you find this: The ConnectionId is in the incorrect format. If so, then your problem may be that you are not using the same machine key on each application server.

See this answer for details on the solution: https://stackoverflow.com/a/43479474/979202