Thank you for your quick reaction Dave, really appreciated! However I do not exactly understand what you mean with { by giving the "*" user basic streaming rights }. Where and how can I do that?
I have 5 users in my TVHeadEnd installation which all have for 'streaming' setting all enabled (Basic, Advanced and HTSP). Further I have set 'Allowed networks' to: 0.0.0.0/0,::/0 for all configured users.