RE: TCP/IP Sockets

["Rich Duzenbury" <rduz@xxxxxxxx>]

No, I think David is correct here.

OS/400 Sockets programming manual:

Usage notes:

1. For sockets that use a connection-oriented transport service (for example, 
sockets with a type of SOCK_STREAM), a returned value of zero indicates one of 
the following

- The partner program has issues a close() for the socket.

- The partner program has issued a shutdown() to disable writing to the socket.

- The connection is broken and the error was retuened on a previously issued 
socket function.

- A shutdown() to disable readingwas previously done on the socket

So, all of my socket reads check for error codes (values less than 0), but also 
the special value of 0 bytes read, and assume the other side unceremoniously 
dumped us off.

> -----Original Message-----
> From: owner-midrange-l@midrange.com
> [mailto:owner-midrange-l@midrange.com]On Behalf Of Bob Crothers
> Sent: Friday, June 11, 1999 6:51 PM
> To: MIDRANGE-L@midrange.com
> Subject: Re: TCP/IP Sockets
> 
> 
> David,
> 
> Close, but not quite.  the read() will return a -1 to indicate an
> error.  At that point, the errno variable (defined in C header file
> errno.h).  Retrieving this value is very easy in ILE/C.  I don't know
> how to get it with RPG.  But I could create a tiny service pgm to
> retrieve it if you would like and nobody comes up with a better way.
> 
> Also note that it depends on how the socket on the other end is closed.
> If a close() is issued, then you will get the -1.  But, if the other
> side ends without actually closing the socket (eg: ctl-alt-del on
> windows), you might not get any indication of a problem.  The
> SO_KEEPALIVE socket option is SUPPOSED to handle this situation, but I
> have never gotten it to work on the AS/400 (at least not up to V3R7).
> 
> Bob
> 
> -----Original Message-----
> From: David Gibbs <David.Gibbs@IL.US.MKS.com>
> To: 'Midrange Mailing List' <MIDRANGE-L@midrange.com>
> Date: Friday, June 11, 1999 4:10 PM
> Subject: RE: TCP/IP Sockets
> 
> 
> >Folks:
> >
> >I'm not 100% sure on this... but I think that, when the remote site of
> a
> >TCP/IP connection disconnects abnormally, a read() (on the other side)
> will
> >return zero.
> >
> >david
> >+---
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