Subject Re: Another "connection forcibly closed by the remote host" problem
Author Scott Moon
Sorry in advance for the wordy post - but there's a lot to talk about.

And you thought this topic had gone away ;-) I've run a lot of tests
in the last couple of weeks, and have made some headway on this
problem. I still haven't solved it, but it's been narrowed down. A
quick recap:

FB SS v1.5.3
Windows Server 2003 Std Edition SP1
Quad Xeon 3.6 GHz Dell server
VMWare ESX Virtual Server running on a Linux OS
VM hosting the Firebird Server is assigned a single CPU, 512 MB RAM, a
10 GB system drive, and a 40 GB data drive.

Any connection to the database is broken after remaining idle for more
than 60 minutes, giving the error message "connection forcibly closed
by the remote host". This is 100% reproducable. It occurs on our
in-house client-server applications, off the shelf client-server apps,
as well as ISQL and Database Workbench.

I have been able to set up a couple of different test environments,
with interesting results. First we created a separate network,
completely independent of our production system. We set up a VMWare
machine also running 2003 server, but instead of Xeons, this one has
dual Pentiums. In this environment, we did not witness a broken
connection in any of several tests, including a connection left open
and idle for over 12 hours.

Next, on our production server we duplicated the VM that our
production DB is hosted on, and ran the following tests:

1) Against a setup identical to our production VM (FB v1.5.3 with
default settings) - same result - connection was broken.

2) As suggested in other posts, I tried changing the CPU_Affinity_Mask
setting in firebird.conf to various settings. No effect. This
surprised me, as the VM thinks it only has 1 CPU. I would have thought
changing that setting to something other than 1 would prevent firebird
from running properly, but it started and ran regardless of the
setting. I made sure to run several tests that would exclude CPU #1.

3) Uninstalled v1.5.3 and installed v1.0.3. The connection was never
broken, even when left open and idle for 24 hours. Reversed the
process - uninstalled 1.0.3 and reinstalled 1.5.3 - connection broke
after 60 minutes.

4) Replaced 1.5.3 with 1.5.2. Same result - broken connection.

5) Replaced 1.5.2 with 2.0. Same result - broken connection.

Conclusion to this point: Something in the combination of FB v1.5.3 +
Xeon + Win2003 + VMWare is causing this. Since Xeon, Win2003 and
VMWare were all present during the successful 1.0.3 test, that points
to something in v1.5.2 forward. I would like to test earlier versions
of 1.5 as well so I can pin-point the version where the problem
started, but I don't have the install kits and can't find them on

I thank everyone for their help to this point, and certainly welcome
any new insights.