I've asked a similar question on the firebird-suppport forum and
there's been no response, so I wonder whether this is more IBO specific.

When installing my app at a customers site, everything worked except
the client app would not receive any event notifications. I suspet a
firewall. I then read that the port used for event notifications is
chosen 'randomly'. The firebird.conf file (on the server) allows you
to change the port numbers of the main Firebird port and the port used
for event notifications.

I've changed both the ports (3060 and 3061) as a test and now IBO
cannot connect. Does IBO need to know the port numbers or is this
just handled by GDS32.dll/FBClient.dll?

TIA