多线程 UDP 程序解决方法

多线程 UDP 程序
在写一个多线程的UDP程序，想在服务器的一个端口上监听数据，每收到一个数据包的时候把数据提取出来丢给一个子线程去处理，处理完之后子线程返回一个返回数据给主程序，然后从该端口上把返回数据发回去，请问该怎么设计才能实现这个目的？怎么让主程序知道子线程已经处理完了呢？
  下面是我的主程序，每收到一个数据就交给ServerSubThread_UDP子线程去处理，现在就是不知道怎么把子线程处理完的数据交给主程序。

Java code

            InetAddress bind_addr = InetAddress.getByName(DNSServer_UDP.BIND_ADDRESS);            serverSocket = new DatagramSocket(DNSServer_UDP.BIND_PORT, bind_addr);            while (bListerning) {                System.out.println("\nUDP Listening...\n");                byte receiveData[] = new byte[DNSServer_UDP.PACKETBUFFSIZE];                DatagramPacket receivePacket = new DatagramPacket(receiveData, DNSServer_UDP.PACKETBUFFSIZE);                // Receive a packet                serverSocket.receive(receivePacket);                // Print client IP and port                System.out.println("Accept one: IP = " + receivePacket.getAddress().getHostAddress() + ", Port = " + receivePacket.getPort());                // Get the data                ONSRecordAction recordAction = new ONSRecordAction();                ByteArrayInputStream bin = new ByteArrayInputStream(receiveData);                ObjectInputStream oin = new ObjectInputStream(bin);                recordAction = (ONSRecordAction)oin.readObject();                                bin.close();                oin.close();                // Process the request in a new thread and keep listening in the port to get new packet                new ServerSubThread_UDP(recordAction, receivePacket.getAddress().getHostAddress(), receivePacket.getPort()).start();            }            }