From: Brian Ford <Brian.Ford@FlightSafety.com>
To: cygwin@cygwin.com
Subject: Re: Socket: non-blocking connect and getsockopt SO_ERROR
Date: Tue, 17 May 2011 14:20:00 -0000 [thread overview]
Message-ID: <Pine.CYG.4.58.1105170912210.3504@PC1163-8460-XP.flightsafety.com> (raw)
In-Reply-To: <1305549799.2447.40.camel@flander>
On Mon, 16 May 2011, Jacob Eiler wrote:
> I am experiencing an issue with getsockopt when running an application
> under CygWin.
>
> The application (Kannel sms gateway) creates a new socket, attempt to
> connect non-blocking to the other host and later calls getsockopt to
> check for errors:
>
> s = socket(PF_INET, SOCK_STREAM, 0);
> ...
> flags = fcntl(s, F_GETFL, 0);
> fcntl(s, F_SETFL, flags | O_NONBLOCK);
> ...
> connect(s, &addr, sizeof(addr))
>
> connect returns EINPROGRESS and the application has a polling thread
> setup to handle timeout and check for changes. In both cases a callback
> function is invoked.
>
> The callback function checks the connection by calling
>
> getsockopt(s, SOL_SOCKET, SO_ERROR, &err, &len)
>
> but it returns 0 and no error - even if the connection was never
> established. Subsequently the application tries to write data to the
> socket - which fails with a "transport endpoint is not connected" error.
>
> The code works just fine on Linux with getsockopt returning an error.
> Any pointer on how to get this working will be greatly appreciated.
The following pseudo code works portably for me on Solaris and Cygwin:
fds.fd = s;
fds.events = POLL_WRITE;
if (Poll(&fds, 1, 0) > 0)
{
len = sizeof(errno);
getsockopt(fd, SOL_SOCKET, SO_ERROR, &errno, &len)
if (errno = 0)
; //connected
}
I think the key is to make sure select/poll returns (as either writable or
with error) before calling getsockopt(SO_ERROR). HTH.
--
Brian Ford
Staff Realtime Software Engineer
VITAL - Visual Simulation Systems
FlightSafety International
the best safety device in any aircraft is a well-trained crew...
--
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prev parent reply other threads:[~2011-05-17 14:20 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-16 12:43 Jacob Eiler
2011-05-16 13:29 ` Corinna Vinschen
2011-05-17 14:20 ` Brian Ford [this message]
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