How to restart during the standard input capture

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Im a car engineer. I try to capture car CAN protocol msg and use Wireshark to analysis. There is no way to capture directly from car. So I write a demo to test whether it can be imported by stdin. And Its works. But I click restart button, pop up error “Unrecognized libpcap format”. I don't want restart whole program every time. What shall I do, or how could I get signal of restart.