var portrange = 45032

function getPort (cb) {
  var port = portrange
  portrange += 1

  var server = net.createServer()
  server.listen(port, function (err) {
    server.once('close', function () {
      cb(port)
    })
    server.close()
  })
  server.on('error', function (err) {
    getPort(cb)
  })
}