Re: [Boost-users] [asio] SSL async_shutdown() never finishes if called when async_read_some() is in progress

Subject: Re: [Boost-users] [asio] SSL async_shutdown() never finishes if called when async_read_some() is in progress
From: Richard Hodges (hodges.r_at_[hidden])
Date: 2018-04-06 14:37:23

On 6 April 2018 at 16:29, Alexander D. via Boost-users <
boost-users_at_[hidden]> wrote:

> On April 6, 2018 9:55 PM, Vinnie Falco via Boost-users <
> boost-users_at_[hidden]> wrote:
> > On Fri, Apr 6, 2018 at 6:11 AM, Alexander D. via Boost-users
> > <boost-users_at_[hidden]> wrote:
> >>>> The only solution I can think of would be to cancel the read
> operation, but there's no portable way in asio to do this.
> >>>
> >>>     sock.next_layer().cancel();
> >>>
> >>> ?
> >>
> >> Per ASIO Reference:
> >>
> >> "Calls to cancel() will always fail with boost::asio::error::operation_not_supported
> when run on Windows XP, Windows Server 2003, and earlier versions of
> Windows, unless BOOST_ASIO_ENABLE_CANCELIO is defined. However, the
> CancelIo function has two issues that should be considered before enabling
> its use:
> >> ..."
> >>
> >> which renders cancel() non-portable.
> >
> > I consider the issues with cancel present in Windows XP and Windows
> > Server 2003 to be sufficiently problematic that it is not worth taking
> > them into account when designing robust network applications (I do
> > develop mostly on Windows). Unless you have a specific business need
> > to support those defective operating systems, I would just ignore
> > them.
>
> Yes, I do need the program to work on at least Windows XP.
>
> However, even if cancel() is used, it is a workaround, not a solution. If
> you run the code I supplied, you'll notice that async_read_some() is
> actually finished with a "stream truncated" error, quite similar to
> "canceling" the read. The problem is on async_shutdown()'s handler not
> being called, and it's not mentioned anywhere in the reference. Why can't
> we shutdown a stream while reading from it (since we can close a socket
> while reading)?
>

In the past, when I have had queries about the inner workings and design
decisions behind ASIO, I have emailed the author, Chris Karloff. I am sure
he is a busy guy but he has taken the trouble to answer helpfully in the
past. It may be worth dropping him a line and asking for a suggestion.

He didn't charge me but having received help twice now, I think it would be
rude of me not to offer him a few hours consultancy if I needed his help
again.

https://think-async.com/Asio/CommercialSupport

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