recv and errno during a connection reset/closed by peert

[Peter A. Castro]

On Wed, 30 Mar 2005, Brian Ford wrote:

> 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).

And I'm saying experience shows to the contrary.

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

We're talking stream, not datagram here.

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

Considering its a very simply solution to a real problem, what makes it a
poor hack?

>> 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).

Yes, and I've never been very happy with it.  If the connection was
closed and there's no more data left to return, I'd prefer recv returned
-1 with ENODATA or ENOTCONN for the errno.  But, it's not likely recv's
semantics will ever be changed.

>> Perhaps it would be better to switch to using read() instead of recv?
> They usually have exactly the same semantics.

Note the word "usually".  Not "always".

> --
> Brian Ford

-- 
Peter A. Castro <doctor@fruitbat.org> or <Peter.Castro@oracle.com>
 	"Cats are just autistic Dogs" -- Dr. Tony Attwood

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