Re: [Quickfix-developers] non logged-on messages

[Caleb E. <cal...@gm...>]

On 8/31/05, Brian Erst <azz...@ya...> wrote:


I would expect that perhaps the first message that gets enqueued due to
> a missing socket connection might have to be PosDup'd (perhaps the
> socket connection disappeared during a send), but on subsequent
> messages the engine would know for sure whether that message had ever
> been sent to the counterparty (even though it may not know whether it
> reached the counterparty). Almost by definition, any message with a
> sequence number greater than the sequence number of last message that
> actually reached a valid socket/network-stream object is NOT a PosDup.
>=20

But you can't know which of your sequence numbers your counterparty is up=
=20
to! Well, you could reconnect, or initiate a Test request and wait for the=
=20
response. But sockets have buffers and networks go down and applications=20
crash, so a successful send() on your end doesn't always mean the other sid=
e=20
will recv() it. So you may have think you have sent several messages that=
=20
your counterparty never got.

In our own home-rolled FIX engine we don't set the PosDup flag unless
> the message is sent due to a sequence-resend request and the sequence
> number is below the sequence number of the last known attempt at
> transmission.


But what if your last-known-attempt counter is too high (as I think I=20
describe above)? I think this behavior is in violation of the spec, which=
=20
says that the PossDupFlag will be set to Y on any message sent in response=
=20
to a resend request. If a counterparty asks you for a bunch of messages, yo=
u=20
shouldn't presume to know better than they do which ones they haven't seen=
=20
yet :-)

--=20
Caleb Epstein
caleb dot epstein at gmail dot com