Client.java

public class Client {
  private final ManagedChannel channel;
  private final GreeterBlockingStub blockingStub;
  private final GreeterStub asyncStub;
  
  public Client(String host, String port){
     channel = ManagedChannelBuilder.forAddress(host, port).usePlaintext().build(); //remove .usePlainText for secure connections
     blockingStub = GreeterGrpc.newBlockingStub(channel); // use it to make blocking calls
     asyncStub = GreeterGrpc.newStub(channel); // or use this to make async calls
  }
  
  public void blockingGreet(String name) {
      logger.info("Will try to greet " + name + " ...");
      HelloRequest request = HelloRequest.newBuilder().setName(name).build();
      HelloReply response;
      try {
        response = blockingStub.sayHello(request);
      } catch (StatusRuntimeException e) {
        logger.log(Level.WARNING, "RPC failed: {0}", e.getStatus());
        return;
      }
      logger.info("Greeting: " + response.getMessage());
  }
  
  public void asyncGreet(String name) {
    
      StreamObserver<HelloReply> responseObserver = new StreamObserver<HelloReply>() {
          @Override
          public void onNext(HelloReply response) {
            logger.info("Greeting: " + response.getMessage());
          }
      
          @Override
          public void onError(Throwable t) {
            Status status = Status.fromThrowable(t);
            logger.log(Level.WARNING, "RPC Failed: {0}", status);
          }
      
          @Override
          public void onCompleted() {
            info("Finished Greeting");
          }
      };
      
      logger.info("Will try to greet " + name + " ...");
      HelloRequest request = HelloRequest.newBuilder().setName(name).build();
      asyncStub.sayHello(request, responseObserver);
        
  }
  
}