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From: andrew@fortress.pubnix.qc.ca (Andrew)
Subject: Re: Detecting dead client in BSD socket
Message-ID: <CMApnn.GxJ@fortress.pubnix.qc.ca>
Followup-To: comp.unix.programmer,comp.unix.bsd
Organization: PubNIX Montreal
X-Newsreader: TIN [version 1.2 PL2]
References: <1994Mar3.154852.24090@il.us.swissbank.com>
Date: Mon, 7 Mar 1994 13:04:34 GMT
Lines: 30
Dwight Lee (leed@il.us.swissbank.com) wrote:
: Is there a way to determine, from the server side, whether a client has
: closed its end of the connection in a BSD socket? If the server attempts
: a write to the dead client, SIGPIPE is received, and that works if
: communication is steady and regular, but I'm wondering if there's a way
: to determine client death/closure at an arbitrary moment.
: If this is a FAQ, feel free to refer me to it, or any in-print books for
: that matter.
: Thank you.
If you've opened your socket in O_NONBLOCK (O_NDELAY), and have posted a
select call on it (IMHO the cleanest way), you will be interrupted with a
read or write select on the socket (Not an exception..haven't figured that
one out yet), and you will either read or write 0 bytes from/to the socket.
Careful inspection of the man page for read/write reveals that reading 0 bytes
indicates a closed socket at the remote end. You can then safely close
yourself down.
From read man page:
set to the value returned in the error message. If a hangup
occurs on the stream being read, read will continue to
operate normally until the stream head read queue is empty.
Thereafter, it will return 0.
--
Andrew Webster
Captain@PubNIX.qc.ca