Date: Fri, 23 Aug 96 15:15:20 EDT From: eischen@vigrid.com (Daniel Eischen) To: hackers@FreeBSD.org, nate@mt.sri.com Cc: nate@rocky.mt.sri.com Subject: Re: Non-blocking I/O on sockets and closed sockets? Message-ID: <9608231915.AA14731@pcnet1.pcnet.com>
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> I need to setup my sockets as non-blocking to avoid some problems, but
> it brings up a problem of determining if the remote end has closed the
> connection. Normally, if you run select() on a FD, and the subsequent
> read() call returns 0 you can assume the socket is dead. However, with
> non-blocking I/O a read of 0 does *NOT* mean the socket is dead.
>
> Will read() return a negative error code on a socket if the socket is
> closed/dead? I've looked in Steven's and in the obvious manpages, but
> nothing jumps out at me.
>
> Here's the code snippet which should explain what goes on.
If the socket is non-blocking, then you should expect errno to be
EAGAIN on a read with no data present. You probably only need
something like this:
[...]
/*
* We may have more data than can fit in lbuff, so read in lbuff
* size chunks.
* XXX - How do we determine if the socket is closed?
*/
do {
i = read(data->stream_sock, lbuff, 512);
if ( i > 0 )
save_data(lbuff, i);
else {
if (errno != EAGAIN)
/* handle error on socket */
;
}
} while ( i > 0 );
}
}
}
Dan Eischen
eischen@pcnet.com
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