private static void sendAsyncRequest(final RpcChannel channel, RpcClient client) {
final CountDownLatch latch = new CountDownLatch(1);
System.err.println("sendRequest " + channel);
SudokuService remoteService = SudokuProto.SudokuService.newStub(channel);
SudokuRequest request = SudokuRequest.newBuilder().setCheckerboard("001010").build();
remoteService.solve(null, request, new RpcCallback<SudokuProto.SudokuResponse>() {
@Override
public void run(SudokuResponse parameter) {
System.out.println(parameter);
channel.disconnect();
latch.countDown();