var eventToPromise = require('event-to-promise');

var createServer = function (port) {
  var server = require('http').createServer();
  server.listen(0);

  // The server will be returned once it has started listening.
  //
  // If an error happened, it will be forwarded instead.
  return eventToPromise(server, 'listening').then(function () {
    return server;
  });
};

// Using plain promise.
createServer(80).then(function (server) {
  console.log('Server listening on http://localhost:80/');
}).catch(function (error) {
  console.error('Server could not start:', error);
});

// Even better using generators!
require('bluebird').coroutine(function *() {
  try {
    var server = yield createServer(80);
    console.log('Server listening on http://localhost:80/');
  } catch (error) {
    console.error('Server could not start:', error);
  }
})();