Re: [ECOS] How to find out if socket closed?

[Grant Edwards <grante at visi dot com>]

On Fri, Jul 11, 2003 at 01:14:57PM -0500, Grant Edwards wrote:

> >> I've been browsing around the old network stack code for a
> >> couple hours now trying to figure out a way to determine if a
> >> TCP connection has been closed by the other end.
> > 
> > Off the top of my head: How about trying a zero sized read?
> 
> The problem is that there is receive data in the socket queue
> waiting to be read.  However, I don't have any room for the
> data, so if the socket hasn't been closed, I need to leave it
> there so that TCP/IP window-szie/flow-control kicks in and
> throttles the other end.
> 
> If the socket has been closed, I need to shut things down.

When the tcp input routine detects a FIN, it calls
socantrcvmore(), which sets the SS_CANTRCVMORE bit in
so->so_state.  

But I sure can't find any sort of system call which will tell
me if that flag is set.  I suppose I could add a custom option
to getsockopt(), but that sort of sucks for all the obvious
reasons.

-- 
Grant Edwards
grante@visi.com

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