Looks like somebody has asked this a while ago on StackOverflow to no avail.

Basically, on the server-side you call:

var result = socket.renegotiate({
  requestCert:true,
  rejectUnauthorized:true
}, function(err) {
  console.error(err);
});

And you will get result === true, but otherwise nothing happens - the callback is never executed.

On the client side, I get the following error:

{ [Error: socket hang up] code: 'ECONNRESET' }

Judging by the test case within io.js, you have a special case for this, but of course I would have no access to constants so I'm not sure what to do here...