Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner@cygwin.com Mail-Followup-To: cygwin@cygwin.com Delivered-To: mailing list cygwin@cygwin.com Date: Wed, 30 Mar 2005 10:18:35 -0600 From: Brian Ford Reply-To: cygwin@cygwin.com To: "Peter A. Castro" cc: cygwin@cygwin.com, Peter Stephens Subject: RE: recv and errno during a connection reset/closed by peer In-Reply-To: Message-ID: References: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-OriginalArrivalTime: 30 Mar 2005 16:18:39.0710 (UTC) FILETIME=[22292FE0:01C53544] On Tue, 29 Mar 2005, Peter A. Castro wrote: > On Tue, 29 Mar 2005, Brian Ford wrote: > > > If you are doing a normal blocking recv without MSG_PEEK, any return of 0 > > should mean a closed connection AFAIK. > > Unfortunately that's not true for all implementation. It's legal for a > zero length data object to be sent. The network simply sends a header > with no payload in it, but it's passed through the network anyways and is > presented to the receiver. The receiver, which might be blocking at the > time, will return from the call and get zero length data, but the > connection is still valid at this point. I've seen AS/400's do just this > sending zero length data to an AIX box. If the sender closes the > connection normally, then subsequent calls to recv return zero with no > indication that the connection is closed. Call it a bug if you want, but > that's how it works. I agree that zero length data can be sent, but only for UDP or datagram based sockets, not for TCP or stream based ones (nothing denotes a message here). Even then, they are only sent by application choice, not just randomly by the OS. Whether a connection is open or closed in this case has little meaning. -- Brian Ford Senior Realtime Software Engineer VITAL - Visual Simulation Systems FlightSafety International the best safety device in any aircraft is a well-trained pilot... -- Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple Problem reports: http://cygwin.com/problems.html Documentation: http://cygwin.com/docs.html FAQ: http://cygwin.com/faq/