I have four threads which read a netcam. Two of those don't connect to the camera.

$ tail motion.conf
thread /etc/motion/kam4.conf
thread /etc/motion/kam_gang.conf
thread /etc/motion/kam_arbeit.conf
thread /etc/motion/kam_computer.conf

$ grep netcam *
kam4.conf:netcam_url http://kam4.intern.smurf.noris.de/oneshotimage1
kam_arbeit.conf:netcam_url http://desk.intern.smurf.noris.de:50381/pic
kam_computer.conf:netcam_url http://zot.intern.smurf.noris.de:50381/pic
kam_gang.conf:netcam_url http://f.raspi.intern.smurf.noris.de:50381/pic

strace shows that the threads for "desk" and "f.raspi" consistently try
to connect to port zero, not 50381.

The config files are otherwise identical.