Well, i actually made already a shared_ptr for the Session type (which is SockHandler class) and it's being passed between all the required classes.

Infact, the server successfully sends to the client the packet, but the socket dies after the async_send.

Put a breakpoint in the destructor for your class that contains the socket.
FIgure out where that class gets destructred, which will destruct the socket.
Now you know what the problem is.

Thank you, i'll work on it.

Updating:

I've been debugging it and destructor is not even being touched.