Hi,
I saw there are many posts on the Internet related to this error. Still also it seams there are different causes.
I am running calibre (0.8.51) headless on a Raspberry Pi. Calibre works fine-I can browse the books via the web interface-still when I try to start and stop calibre from ssh terminal I get that error. I remember I used to be able to do that before. I really can't imagine what went wrong. Calibre start correctly at booting with this
script.
Any suggestions on where to start/look to solve it?