Ubuntu lists USB devices by default under /dev/ as ttyUSBx where x is a number starting 0. Issue with this is if USB devices are swapped to a different port, it’s not clear with ttyUSBx device relates to which physical USB device.
There are a few ways to change settings to point to the correct USB Device. I’ll list to 2 most common ways. The below is an examples for an RFXTrx433 USB Transceiver, but the process works the same for any other USB device.

Option A

1. Point the app to the device’s serial id. Run this in a terminal:

   ls /dev/serial/by-id/

2. This will list all serial USB devices. Pick the one that you need to communicate with and set its address in your app, e.g.

   /dev/serial/by-id/usb-RFXCOM_RFXtrx433_A1XETWB5-if00-port0

Option B

1. 1. Run this in a terminal:

      udevadm info -a -p $(udevadm info -q path -n /dev/ttyUSB0)

      (if necessary replace ttyUSB0 with ttyUSB1)

   2. You need to locate the block where it gives you the correct value for your device, ATTRS{manufacturer} and/or ATTRS{product} and take note of the ATTRS{idVendor} ATTRS{idProduct} and ATTRS{serial}:
      
   3. Edit the following file with your preferred editor:
      /etc/udev/rules.d/99-usb-serial.rules and add this line:

      ACTION=="add", ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6001", ATTRS{serial}=="A1XETWB5", SYMLINK+="RFXTrx433"

   4. Replace the values in ATTRS{idVendor} ATTRS{idProduct} and ATTRS{serial} with the ones you found in previous step, replace RFXTrx433 with a name that makes sense to you. Save and Exit
   5. Run this in a terminal:

      sudo udevadm control --reload && sudo udevadm trigger

   6. You should then have a new device listed in /dev matching the name you provided after SYMLINK. To confirm, run this in terminal:

      ls /dev/RFX*

      (replace RFX with the name you provided after SYMLINK)

   7. Enter the device’s “new” address in your app, e.g.

      /dev/RFXTrx433

Now it does not matter which USB port your device is connected to, it will always be found.