I get the message “Could not use network connection. The port number is already in use.”
Open the Preferences dialog on your main device and change the Port No. in the Smartphone Connection section.
This error appears when the same port for connecting in Companion mode is used for another service, such as an online game.
Changing the Port No.
1. Open Preferences.
2. Select Smartphone connection.
3. Change the Port No under Main device settings and click OK to apply the change.
What is a Port No.?
Port numbers are used by software to communicate with external devices over a network.
Each different program must use a different number so that your device can identify the individual program to provide service for device sending the incoming connection.
For instance, if an online game is already using Port No. 32035 on your computer, the same number cannot be used to connect Clip Studio Paint in Companion mode.
In a case like this, it is a good idea to test different ports by making small changes to the Port No. (for example, to 32036, then 32037, and so on) in the Preferences menu.