Are web sockets a web browser feature, developed and evolving as the browser developers want, or this feature dependent on the OS version?
For example, can I use this feature in JavaScript in IE and other browsers from Windows 8 only?
If it is a browser feature, which versions is it stable in Chrome, Mozilla, Opera?
webSocket is implemented in browsers (not in the underlying OS). It is built on top of TCP/IP which comes from the OS.
You can see which versions of which browsers support webSockets here:http://caniuse.com/#feat=websockets
2