Websocket server always returns close state,but works fine in localhost

I get the source code of a great webrtc demo from

https://github.com/webRTC/webrtc.io-demo

and the demo site is: webrtc.dennis.is

It works fine when I start a local node server, but when I upload the demo to a node server online( www.appfog.com ), I come into an unexpected bug which says :

WebSocket connection to 'ws://talktosomeone4.ap01.aws.af.cm/' failed: Unexpected response code: 200 talktosomeone4.ap01.aws.af.cm:1

At first I think maybe it's caused by missing port,so I try to complete the websocket url by adding port like :

ws://talktosomeone4.ap01.aws.af.cm:8080/

or the port I get from serve: process.env.PORT, the error message is gone but the websocket.onopen is never fired , it always fires the onclose event. In result, the webrtc doesn't work.

What's the problem? What should I do?

I'll appreciate it for your kind help!!!