Re: [Dclib-devel] non blocking patch

[Davis K. <dav...@us...>]

I have been testing out this patch for a while (on windows and linux) and
trying to think if there are any funny corner cases.  I also spent a lot of
time a few years ago trying to work something like this into the connection
object and ended up giving up but I forgot why until just now.

Anyway, I found a problem related to sending data via send().  The problem
is that send() will block, even if select() says it won't, if you give it a
buffer larger than a certain value (the value depends on your platform and
isn't at all portable).  Linux allows you to set the MSG_DONTWAIT flag which
fixes the issue but MSG_DONTWAIT isn't a POSIX thing and so isn't portable
to other platforms.

See http://www.opengroup.org/onlinepubs/009695399/functions/send.html for
example.

I think the only safe way to get this to work is to create the socket in
non-blocking mode to begin with.  Then we don't have to worry about
functions blocking when hidden buffer size limits are hit.  So I think that
would mean making a new object that explicitly represented a non-blocking
socket.

I'm not in any dire need for non-blocking sockets so I probably won't be
implementing this any time soon.

You might also want to check out the asio library (
http://think-async.com/Asio/).  It has a whole lot of support for varous
kinds of networking modes.  It is also, in all probability, the networking
library that will eventually make it into C++ standard library.  So it might
be worth learning just for that reason :)

Cheers,
Davis

On Fri, Apr 17, 2009 at 7:35 PM, miguelg50 <mig...@ve...> wrote:

> Davis,
>
> Attached is the patch for the non-blocking socket changes I've made. I hope
> it is useful.
>
> Miguel