[asio-users] Send / receive separately question

[Michael IV <exp...@gm...>]

Hi All. I have probably a stupid question to ask.But I am ASIO noob so
please bear  with me.

I have a server which sends some data in a loop constantly. But at the same
time,the server should also be able to receive a data from the client. The
data from the client arrives occasionally.What I did till now, was
activating send loop right after connection accept,then send the data
synchronously and receive the data synchronously right after send. But then
I found it degrades server's performance dramatically,because asio::read
blocks each time that there is nothing to receive (because the client is
not sending the data constantly). So  I want to separate asio::write from
asio::read routines.I found this answer to a similar problem:

https://stackoverflow.com/questions/33666662/boost-asio-networking-separate-send-and-receive

What I don't understand here is: if both send and receive async  methods
are being called always,how it doesn't cause to a stack overflow. I mean,
every time async read is called,but there is nothing to read yet, what
happens after the hood? Is this really the way to do what I asked? Thanks!