[Boost-users] How to design proper release of a boost::asio socket or wrapper thereof

Subject: [Boost-users] How to design proper release of a boost::asio socket or wrapper thereof
From: Christopher Pisz (christopherpisz_at_[hidden])
Date: 2017-04-05 20:32:10

I am making a few attempts at making my own simple asynch TCP server using
boost::asio after not having touched it for several years.

The latest example listing I can find is:
http://www.boost.org/doc/libs/1_54_0/doc/html/boost_asio/tutorial/tutdaytime3/src.html

The problem I have with this example listing is that it cheats and it cheats
big, by making the tcp_connection a shared_ptr, such that it doesn't worry
about the lifetime management of each connection.

I am worried about the lifetime management of each connection. I figure the
natural thing to do would be to keep some collection of tcp_connection
objects or pointers to them inside tcp_server. Adding to that collection
from the OnConnect callback and removing from that collection OnDisconnect.

Note that OnDisconnect would most likely be called from an actual Disconnect
method, which in turn would be called from OnReceive callback or OnSend
callback, in the case of an error.

Well, therein lies the problem.

Consider we'd have a callstack that looked something like this:
tcp_connection::~tcp_connection
tcp_server::OnDisconnect
tcp_connection::OnDisconnect
tcp_connection::Disconnect
tcp_connection::OnReceive

This would cause errors as the call stack unwinds and we are executing code
in a object that has had its destructor called...I think, right?

I then thought to myself, well I could flag the tcp_connection as
disconnected when it disconnects and then on some timer on the tcp_server,
go through its collection and start deleting disconnected tcp_connection
objects, but then the timer could fire after the flag is set, but before it
returns from a OnReceive where an error occurred and I Disconnected as a
response.

I imagine everyone doing server programming comes across this scenario in
some fashion. What is a strategy for handling it?

I hope the explanation is good enough to follow. If not let me know and I
will create my own source listing, but it will be very large.
 

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