Yup.  I verified, and I get return value of -1 for the read, and errno
is set to EAGAIN.  This is on the first read after the other end of the
connection has been SIGKILLed.  I do NOT get a return value of zero,
that was a typo in the original post.

On Tue, 9 Dec 2003, Bill Studenmund wrote:

> On Sat, Dec 06, 2003 at 07:30:45AM -0800, Paul Goyette wrote:
> > How does one tell if a TCP socket has been disconnected without trying
> > to write to the socket?
> >
> > If the remote end closes the socket normally, all is OK.  But if the
> > remote process is SIGKILLed, my listener is notified via select(2)
> > that the socket is available for reading.  Yet when I read from the
> > socket, I get zero data returned and errno=EAGAIN.  Since the same
> > errno is returned if the socket is empty, how can I distinguish that
> > that remote end is gone?
>
> Uhm, getting back zero data means you hit the end. If there is nothing to
> read but the connections is still alive, you'll get -1 and errno will be
> EAGAIN.
>
> From man read:
>
> RETURN VALUES
>      If successful, the number of bytes actually read is returned.  Upon read-
>      ing end-of-file, zero is returned.  Otherwise, a -1 is returned and the
>      global variable errno is set to indicate the error.
>
>
> Note that errno only matters if you get back a -1.
>
> Take care,
>
> Bill
>

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