listenFD

[isaacs]

Re-implement listenFD in master.

Ok for windows to raise ENOTSUP if it's too hard to implement, but it must be a clean failure.

[piscisaureus]

suggestion

• new net.Server({fd: 3}).listen()
  the argument to listen() would be optional if the socket is already bound. And if it is unbound, then this API is kinda pointless.
• Check if new net.Socket({fd: 3}) works, and if it doesn't, fix it.

[isaacs]

What about new net.Server().listen({fd:3})?

[indutny]

I like .listen({fd:3}).

[piscisaureus]

Augment Server.prototype._listen2 (https://github.com/joyent/node/blob/b9e40fbaacc60de562481b764b0e78bf021f7cfa/lib/net.js#L858-897):

1. add an fd argument
2. if fd is present, call uv_guess_handle(fd), depending on the result create a PipeWrap or TcpWrap. Similar to: https://github.com/joyent/node/blob/b9e40fbaacc60de562481b764b0e78bf021f7cfa/src/node.js#L284-319

Then change listen and Server.prototype.listen to correctly handle {fd: x}.