Pretty much every modern websockets Javascript library you use these days will provide fallback mechanisms to flash or long polling to provide the same features. Take a look at the supported browsers for Socket.io and its a much larger list then the one you've provided.
They're not sockets, they're WebSockets, and they require a custom HTTP server setup just to open a socket connection to a service.
This means that I can't do something that should be really simple -- like open a VNC connection to a remote server -- without first configuring an HTTP WebSocket proxy.
