WebSocket-Powered Rails Applications 200 error

i try to run this tutorial in local and got
WebSocket connection to 'ws://localhost/auctions/3' failed: Error during WebSocket handshake: Unexpected response code: 200

I’m using rails 4, faye-websocket to establish websocket connection. I have no idea 200 error mean. Can anyone help?

This is the tutorial I try to follow: https://code.tutsplus.com/courses/websocket-powered-rails-applications/lessons/beginning-websockets-for-the-server