This question already has an answer here:

I have an issue with trying to open a USB device's serial port with pyserial. It seems that as fast as I connect the device, /dev/ttyACM0 is used by some random process.

ModemMana  851        root 8u  CHR  166,0  0t0  16925693 /dev/ttyACM0
gmain      851   879  root 8u  CHR  166,0  0t0  16925693 /dev/ttyACM0
gdbus      851   884  root 8u  CHR  166,0  0t0  16925693 /dev/ttyACM0

If I wait a few seconds it works fine. This however forces me to have a 10 sec timeout on my application which is real bummer. What is ModemMana, gmain and gdbus doing with the serial port?? Is this normal behaviour?

marked as duplicate by Kusalananda, Stephen Harris, garethTheRed, Gilles, Thomas Dickey Jul 24 '16 at 23:24

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • See askubuntu.com/questions/216114/… – jofel Jan 21 '15 at 15:29
  • @jofel yes. The problem is that I am building an application for users so I can't be asking them to un-install or modify already software on their system. – Pithikos Jan 21 '15 at 15:32
  • A fast solution is to continuously try to open the serial port while hiding the exceptions. Eventually it will succeed.. – Pithikos Jan 21 '15 at 17:47