--- In firebird-support@yahoogroups.com, Olivier Mascia wrote:

> when playing in the > 300 attachments range (could be 350 or 400, does not seem precise), I have seen new attachments denied (-904, code 335544375) and this logged in firebird log:
>
> XNET error: Server failed to respond on connect request
>
> What kind of limitation could this be?

Listener process was not in time when launched worker process to handle new connection.
This is possible when there is a lot of simultaneous requests for a new connections.
fbclient waits for (10 sec, iirc) response from a server on initial packet and if wait was timed out message above is logged at firebird.conf.

It was improved recently, see
http://tracker.firebirdsql.org/browse/CORE-2769

Regards,
Vlad