Subject Events and server ports
IB 6.01 on Linux 2.18, D4 IBO 3.6ca

IB comunicates via port 3050.

IB works fine through a firewall that has 3050 open. But then, when
the 'RegisterEvents' method gets called nothing goes anymore.

A tcpdump reveals that IB obviously tries to open another ip
connection for event messaging which is different than 3050. E.g. I
found ports 178x being used counting up with every 'RegisterEvent'

Does anyone know which range of ports need to be accessible for IB in
order make use of events in a restricted network setup?

There are NO problems at all in a non-restricted network scenario!