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You should be aware that Intiface Central is beta/early access for Android if you didn’t already know that.
Your call stack is the same as in the following post about port collisions when starting the server. Maybe you have another app using the same port?
Many installed apps start background services that may open ports even if you haven’t started any app yourself. I assume that you have to go into Android development mode to manually run commands to verify that port 12345 isn’t already used, or download an app that has that same capability.
Anyways, you have a reported issue on github and the app is beta/preview so my guess is that you just have to wait. There are other issues that have been addressed and that will be in v2.4.1 so there is a new version in the works that may or may not include a fix for your issue.
Sorry, it was many years ago since I used development mode on Android so I don’t remember. However, it should be easy enough to google it. Otherwise I would consider looking for a trustworthy app that can show operating system information like used ports and associated processes.