public class NioNonBlockingEchoServer {

   public static void main(String[] args) throws IOException {
       ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
       serverSocketChannel.configureBlocking(false);
       serverSocketChannel.bind(new InetSocketAddress(7000));

       while (active) {
           SocketChannel socketChannel = serverSocketChannel.accept(); // non-blocking
           if (socketChannel != null) {
               socketChannel.configureBlocking(false);

               ByteBuffer buffer = ByteBuffer.allocate(1024);
               while (true) {
                   buffer.clear();
                   int read = socketChannel.read(buffer); // non-blocking
                   if (read < 0) {
                       break;
                   }

                   buffer.flip();
                   socketChannel.write(buffer); // can be non-blocking
               }

               socketChannel.close();
           }
       }

       serverSocketChannel.close();
   }
}