FreeTDS Development Group

[LacaK <lacak AT zoznam.sk>]

> > I can not check status of connection before I send query?
> You cannot check the status of the connect before you send the query
> because the status changes only when the connection is used.
>
> Consider what it looks like at the TCP/IP level.  The client went to
> sleep, and then woke up.  Meanwhile, the server disconnected.  From the
> client's perspective, nothing has changed: errno is still the same, the
> TCP/IP socket still appears valid.  There's no syscall to test whether
> a socket is (still) connected to its peer.  The only way to find out is
> to try to *do* something, which means reading or writing.
>
> Actually, the "went to sleep" part is unnecessary.  How does one
> terminate a connection?  By closing the socket, right?  Does that cause
> a message to be sent to the peer, interrupting it, saying "the
> other party just closed the connection"?  No.  The peer learns of the
> disconnection when it next tries to read or write to its end.
>
> There's no inconsequential "are you there?" message in TDS, either.
> DB-Library can't send a message on your behalf to determine the
> connection status, because the state of the TDS session is under the
> application's control.
>
> So the only possible solution is to learn by doing: call the next
> db-lib function, get the error, and test it with dbdead().  It seems
> clunky, but it has the distinct advantage of not relying on Action at a
> Distance.
>
> Hope that clarifies things a bit.

Thank you guys very much for replies.
I will try do it as you suggest ...
-Laco.