This is an implementation of the official WebSocket API + Node.js.
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Assuming you have Node.js installed on your machine, just clone the repository and run node server.js or npm start.
Then open index.html in your browser.
You shouldn't even need a web server, but I'd recommend using one anyway. If you have python installed it's just one command away, e.g.: python -m SimpleHTTPServer. Then go to http://localhost:8000.