Sometimes my client can't receive data

Hello, everyone ! I'm using openssl as client in blocking mode , i have a problem . Sometimes my program can't receive data , and acctually server has been sent the data to me. I can only receive the data by sending another request . Then the data i expected arrived with a new data sent by

My client can not receive data in blocking mode

Thank you very much for your reply . My server running on centos 7.5 . And client running on windows 10 . The data seems be cached on the server and not be sent out. Dose centos have the same problem? I'm not sure what the problem is . I would really appreciate if you have any Suggestions.