Tvheadend

Check firewall. It seems that it does not forward UDP packets.

It works, I have a working setup here. Wrong parameters cause it to not work though.

Well, double fail on my side:

tvheadend needs UDP packets being send from the SAT>IP to tvheadend
I had to allow UDP connections from the AVM DVB-C UDP ports 5000/5001 to the tvheadend server IP to make it work again.¶

Why streaming with the same rtsp links would work when entered in VLC directly (tvheadend server machine)? Beats me :(
However, Kodi as client works just fine!

Using the M3U files from the "play" link doesn't work at all
For debugging I used the "play" links from Configuration > DVB Inputs > Services which unfortunately don't work at all (even after I got my overall setup to work again). Therefore it didn't even work (from my debugging perspective) when both tvheadend server and DVB-C input would be in the same /24 network.¶

So, lesson learned: use Kodi for debugging the individual TV streams, not VLC and the M3Us provided by tvheadend. :(

I hope this will help someone stumbling over the same problems as me some day...

playlist for client can be found on
http://tvh.dns.ip:9981/playlist/channels
depend on security authentication settings /plain digest/
http://user:pass@tvh.dns.ip:9981/playlist/channels

if user have enabled persistent authentication
http://user:pass@tvh.dns.ip:9981/playlist/auth/channels

Steffen Breitbach wrote:

Using the M3U files from the "play" link doesn't work at all¶

It should work. But the lifetime of the authentication ticket is limited to 5 minutes, so you cannot use those files after this.

Use user:passwd authentication or the persistent authentication code.