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From: pyk@sv.vtcom.fr (Pierre-Yves Kerembellec)
Newsgroups: comp.unix.bsd.freebsd.misc,comp.os.linux.development.apps
Subject: Re: Checking for a closed socket connection
Date: Fri, 26 Jan 1996 09:02:48 GMT
Organization: Solutions Vocales
Lines: 27
Message-ID: <4ea6cd$mq8@nestor.sv.vtcom.fr>
References: <NEWTNews.822505959.29723.jalvarez@sundev.uno.com> <4e7l8n$50f@charm.il.ft.hse.nl>
Reply-To: pyk@sv.vtcom.fr
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Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:12871 comp.os.linux.development.apps:11252
robert@il.ft.hse.nl (Robert Klep) wrote:
>jalvarez@uno.com:
> >Is there a simple way to test a socket descriptor for a closed
> >connection (e.g. if the connection to the other side was lost
> >and is no longer valid) ?
>read() to/write() from it and see if the function returns a -1 :)
You can also use a "setsockopt" system-call and set the
SO_KEEPALIVE flag for that particular socket : your process
will receive a SIGPIPE if the peer hangs up
(of course, it's your duty to handle that signal properly)
By the way, the "read" system-call won't return -1 in any case (trust me !)
A more secure code would be something like that :
...
status = select(...)
if (status>0)
{
size = read(...);
if (size<=0) return(SOCKET_DOWN);
}
...
(note the '<=' and not just '<')
Pierre-Yves