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Date: Wed, 30 Mar 2005 10:46:40 -0600
From: Brian Ford <ford AT vss DOT fsi DOT com>
Reply-To: cygwin AT cygwin DOT com
To: "Peter A. Castro" <doctor AT fruitbat DOT org>
cc: cygwin AT cygwin DOT com, Peter Stephens <ptfoof AT sbcglobal DOT net>
Subject: RE: recv and errno during a connection reset/closed by peert
In-Reply-To: <Pine.LNX.4.60.0503291711560.736@gremlin.fruitbat.org>
Message-ID: <Pine.CYG.4.58.0503301029410.3732@fordpc.vss.fsi.com>
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X-OriginalArrivalTime: 30 Mar 2005 16:46:44.0332 (UTC) FILETIME=[0E461AC0:01C53548]

On Tue, 29 Mar 2005, Peter A. Castro wrote:

> On Tue, 29 Mar 2005, Brian Ford wrote:
> > On Tue, 29 Mar 2005, Peter Stephens wrote:
> >> I have thought about your suggestion and it makes a lot of sense.
> >>
> >> It seems like your suggestion would be very portable.  A good
> >> suggestion and the most likely route for me at this point.
> >
> > Not to me.  Maybe I'm missing something, but it seems you are going to a
> > lot of effort to poorly recreate poll/select?
>
> Why?

A zero length return on a stream socket always means that the peer has
closed its socket for writing.  It may, however, still be open for
reading (I don't remember the syscalls for doing such, but it can be
done).

A zero return on a datagram socket always means that a zero length
message has been received.

Counting zero returns is a poor hack at best and makes no sense to me
since it never gives you any more information.

> If you are doing sequential, non multi-plexed, reads why do poll or
> select?

You don't need to.

> Sitting in read is more optimal and the read should return
> either data or an error.

Ok.

> The flaw in recv is that it returns a non-error non-data status.

It's not a flaw, it's the design (see above).

> Perhaps it would be better to switch to using read() instead of recv?

They usually have exactly the same semantics.

-- 
Brian Ford
Senior Realtime Software Engineer
VITAL - Visual Simulation Systems
FlightSafety International
the best safety device in any aircraft is a well-trained pilot...

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