For completeness, here is a log to show that Rhythmbox does indeed make a HEAD request:
HEAD /ueberklang/ueber220608.mp3 HTTP/1.1 Host: listening.at:8000 User-Agent: gnome-vfs/2.22.0 neon/0.25.4 Keep-Alive: Connection: TE, Keep-Alive TE: trailers HTTP/1.0 400 Bad Request Content-Type: text/html <b>unknown request</b> -- Rhythmbox cannot download some podcasts (port 8000) https://bugs.launchpad.net/bugs/247123 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs