My solution for the problem:
to cut a long story short: I can connect again. What I did was stopping apparmor:
Next step will be of course configuring apparmor correctly.
sudo /etc/init.d/apparmor teardown
My problem was the same as described multiple times here on this thread. Error "SL0x12" while connecting via browser, no narport.txt when using the junipernc script.
So propably it is not a problem of the used jdk - which explains, why there was no difference in using openjdk, sun126.96.36.199 and now sun188.8.131.52.
So - if you got a "SL0x12" try disabling apparmor.