What is it

Due to the stateless nature of UDP there's no standard way to send requests and obtain responses for them. You would have to send a request and then listen for the 'message' event and somehow figure out which message is a response to your request.

This is why the Controller class was introduced. It allows you to create requests and wait for a response, similar to the standard way of fetching a resource, making the development of your apps a lot easier.