tester/src/main/java/org/apache/james/jspf/tester/UDPListener.java

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 * 'dnsjava-2.0.5'. This original is licensed as follows:       *
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package org.apache.james.jspf.tester;

import java.io.IOException;
import java.io.InterruptedIOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

public final class UDPListener implements Runnable {

    private final static class UDPResponder implements Runnable {
        private ResponseGenerator responseGenerator;

        private DatagramSocket sock;
        private InetAddress addr;
        private int port;
        private byte[] in;

        private UDPResponder(DatagramSocket sock, InetAddress addr, int port, byte[] in, ResponseGenerator rg) {
            this.sock = sock;
            this.addr = addr;
            this.port = port;
            this.in = in;
            this.responseGenerator = rg;
        }

        public void run() {
            try {
                DatagramPacket outdp = null;
                byte[] response = responseGenerator.generateReply(in, in.length);
                if (response == null)
                    return;
                if (outdp == null) {
                    outdp = new DatagramPacket(response, response.length,
                            addr, port);
                } else {
                    outdp.setData(response);
                    outdp.setLength(response.length);
                    outdp.setAddress(addr);
                    outdp.setPort(port);
                }
                sock.send(outdp);
            } catch (IOException e) {
                System.out.println("UDPResponder(" + addr.getHostAddress() + "#" + port + "): "
                        + e);
            }
        }

    }


    
    private final InetAddress addr;

    private final int port;

    private ResponseGenerator responseGenerator;

    UDPListener(InetAddress addr, int port, ResponseGenerator rg) {
        this.addr = addr;
        this.port = port;
        this.responseGenerator = rg;
    }

    public void run() {
        try {
            DatagramSocket sock = new DatagramSocket(port, addr);
            final short udpLength = 512;
            byte[] in = new byte[udpLength];
            DatagramPacket indp = new DatagramPacket(in, in.length);
            while (true) {
                indp.setLength(in.length);
                try {
                    sock.receive(indp);
                } catch (InterruptedIOException e) {
                    continue;
                }

                byte[] local = new byte[indp.getLength()];
                System.arraycopy(in, 0, local, 0, indp.getLength());
                Runnable runnable = new UDPResponder(sock, indp.getAddress(), indp.getPort(), local, responseGenerator);
                
                new Thread(runnable).start();
            }
        } catch (IOException e) {
            System.out.println("UDPListener(" + addr.getHostAddress() + "#" + port + "): "
                    + e);
        }
    }

}