helloserver.java

static class GreeterImpl extends GreeterGrpc.GreeterImplBase {

  @Override
  public void sayHello(HelloRequest req,
                       StreamObserver<HelloReply> responseObserver) {

    HelloReply reply = HelloReply.newBuilder().setMessage("Hello " + req.getName()).build();
    responseObserver.onNext(reply);
    responseObserver.onCompleted();
  }
}