[Boost-users] Which socket read get first when both asio::async_read and asio::read are active?

Hi, I have a socket server program to activate in asio::async_read for receive any messages initiated from client. But when the server sends a message to the client, it uses sync write and flowing a sync read (asio::read) to immediately receive the response. The issue I can think of is who will get first read when both asio::async_read and asio::read are active? Thank you. Kind regards.