Administration - Installation - Core: Error starting Java Server

Hello,

i can't get the Java Server running. I get the following error on executing
java -Dfile.encoding=UTF-8 -jar ilServer.start

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index 1 out of bounds for length 1
        at de.ilias.ilServer.handleRequest(ilServer.java:102)
        at de.ilias.ilServer.main(ilServer.java:82)

I created ilServer.ini as indicated in the documentation, made sure that it is accessible by the webserver and its settings match those of the ilServer.properties file.

Can anybody please clue me where to start looking for a fix?
I'm on Ubuntu 18.04 and Ilias 6.6, anything else on the Ilias Instance is just working fine.

Any help would be very much appreciated!

Kind regards, Fred