Andrej van der Zee <mavdzee@yahoo.co.uk> wrote:
> I was wondering how I can find out with ASIO whether a
> connection is broken. I have a client connected to the
> server that continuously streams data.

The canonical way to consistently detect broken TCP
connections is to always have a read on the socket - it
will return 0 on broken connection (in usual BSD sockets
type reads - I would expect an appropriate error parameter
set in ASIO). Since you're doing async operations this is
pretty easy.

Many times a write will only buffer the data (at the OS /
TCP driver level), and an error is not detected until a
later write (and if the client socket is in a "half
shutdown" mode, it might be quite a while before the TCP
keepalive timer pops and the socket is fully destroyed).

This is absent special ASIO capabilities - if ASIO is
doing a read "on your behalf", then the problem is the
"not completely destroyed connection", which is an OS /
TCP "feature" and nothing that ASIO can help with. I
haven't found specific details relating to this in ASIO,
but that may only be because I haven't read enough of the
ASIO documentation.

Chris K (or others), clarifications, corrections, or
comments?

You test for a disconnection with Asio the same way you would with BSD sockets - you need to leave a long-running read operating going.

Check out this post from the Asio-users mailing list: http://osdir.com/ml/lib.boost.asio.user/2006-11/msg00035.html

Richard

Cliff

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