Java套接字编程回调

Question

I have created a class library project "Communication" which is for communicating using UDP socket programming.

This communication will be invoked from application and made communication as always open and ready to accept using thread.

When ever data has to be sent, Since Application has the Communication object, its simple and easy to access.

But whenever a data is received, I want data to be sent to application.

refer pic below.

How to achieve this?, delegates?

Answer 1

Make an interface such as this:

interface Notifyable {
  void notify(DatagramPacket p);
}

and let your Application implement it.

Then give your Communication class the reference to Application and whenever you receive data, call the notify method.

Answer 2

UDP communication should work the same in both directions. There is no asymmetric client/server nor sender/receiver. Your "Application" and "Communication" should work the same way.

Both can send messages and both can receive them in the same manner.

In other words, you should have written this code already on the listening side, you just need the same listening side on the "Application"

Answer 3

What you are describing fits perfectly into http protocol. In HTTP the server receives a request and sends a response to the client. So unless you have a specific requirement to use UDP the simplest servlet would give you a desired behavior - Server is always up and available and upon receiving an HTTP request your servlet would send a response. So, just read up how to get some Web Server or application Server and create a servlet and you are all set. For simplicity I would recommend using Apache Tomcat as your server.