Affected versions identified: 2.5.8, 2.5.7 and 2.5.5 all as SuperClassic running on dedicated server with Debian distribution.

I'm going through a situation where applications can not connect to Firebird. At a certain point, suddenly, Firebird does not accept remote connections.

Connecting locally, via isql, it is possible to access Firebird and perform queries normally, but not remote. No error messages are identified in the Firebird log or operating system logs. As a workaround, we only restart Firebird and it works normally, receiving local and remote connections. We  bserve that if we return Firebird to version 2.5.0 these issue stop happening.

I have enabled the audit to try to identify what is happening at the time of the freeze,  however in each freeze I observe a different set of sql commands, there is not indicating what can

 be causing the issue and also there are no error or warning messages on audit log.

Has anyone gone through this or have any suggestions on how can I identify what might be causing this freeze?

I saw similar behaviour in 2.5.8 on Linux. It is reported as bug CORE-5757 (http://tracker.firebirdsql.org/browse/CORE-5757?subTaskView=unresolved) and is fixed for 2.5.9.

For me it seemed to be related to using database events, but the comments on the bug from the developers suggest it is not related.

I have patched 2.5.8 packages for Debian stretch which you could try.

Hamish