Re: Is it possible to detect TCP session term without reading pending data?

From: Andrei Voropaev (avorop_at_mail.ru)
Date: 04/16/04 

Date: 16 Apr 2004 07:25:53 GMT

On 2004-04-15, aprotopa <aprotopapas@yahoo.com> wrote:
> Hi all -
> I have an application which should only read from a TCP socket if
> condition X is true. But the application should also be able to
> detect if the TCP peer closed the connection from his side.
> The problem happens when condition X is false while the peer
> terminates the connection, but there is data pending to be read on the
> socket. In that case, poll() becomes useless to me because it only
> tells me that there is data to read, not that the connection has been
> terminated.
> Does anyone know a usage of poll() or some other system function
> that would give the application the ability to detect the closed
> connection in this special case?
> I work mostly on Solaris, but ideally I would like to find a
> portable solution to this problem.

Really, it all depends on your specific situation. For example, if you
still write while your X is false, then after your peer has closed
connection 'send' shall return EPIPE (of course if you use MSG_NOSIGNAL
flag). Also poll may set POLLHUP flag. If your application does not
write and your X might be false for long time, then it's better to read
from socket and discard incoming data (your protocol allows discarding,
right ? :)

Andrei

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