Please use https://github.com/ninenines/cowboy/tree/master/examples/websocket instead.
To compile this example you need rebar in your PATH.
Type the following command:
$ rebar get-deps compile
You can then start the Erlang node with the following command:
./start.sh
Then point your browser to the indicated URL to open a websocket client. Not all browsers support websockets. It was tested with Chromium.