Cal 3.2.1 Content Server shows only "Receive OK" when accessing from iOS

Hi friends,

i recently installed Calibre 3.2.1 and started the Content Server. Access via localhost is fine.. but when accessing via WLAN from an iOS 10.3.2 ( iPhone 7plus and iPad4 ) i only get back a plain site saying "Receive OK"

e.g. 192.168.0.3:8080... also 192.168.0.3:8080/mobile only brings back "Receive OK"

Same with Safari and Firefox for IOS

any hints ?

byby
Freddy