Why synchronous producer does not receive response from broker?

[SuoNayi]

Hi all,
   I have just found that my synchronous producers do not receive any data from 
broker.
   As far I know, the synchronous producer should receive the acknowledgement 
from broker 
   to ensure that messages are delivered successfully or not.
   But why kafka broker does not answer the request of producer with 
acknowledgement ?
   Is there any other way for producer to ensure the successful delivery?