@Akira_Hayakawa_Atsurae Thank you. It solved my problem.

But the NE will not work anymore.

Thank you for explaining. I'm developing my VPN app currently. I can hardly debug my application now. Condition: I connect my phone\iPad with cable to my computer When I clicked debug run, everything worked well. After I clicked the connect button in my application, the VPN tunnel connected. Then I lost connection to my device. The debug was interrupted by this. And this will 100% happen. So I feel the devices were not connected to the computer by cable. This is why I ask this question.