import java.io.IOException;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.channels.DatagramChannel;
public class UDPTimeServer {
public final static int DEFAULT_PORT = 37;
public static void main(String[] args) throws IOException {
int port = 37;
ByteBuffer in = ByteBuffer.allocate(8192);
ByteBuffer out = ByteBuffer.allocate(8);
out.order(ByteOrder.BIG_ENDIAN);
SocketAddress address = new InetSocketAddress(port);
DatagramChannel channel = DatagramChannel.open();
DatagramSocket socket = channel.socket();
socket.bind(address);
System.err.println("bound to " + address);
while (true) {
try {
in.clear();
SocketAddress client = channel.receive(in);
System.err.println(client);
long secondsSince1970 = System.currentTimeMillis();
out.clear();
out.putLong(secondsSince1970);
out.flip();
out.position(4);
channel.send(out, client);
} catch (Exception ex) {
System.err.println(ex);
}
}
}
}