An electronic device includes a network interface port, a processing unit, a network card, a serial interface, and a microchip. The network interface port connects to a debugging host or connects to an external network. The processing unit is connected to the network interface port. The network card is connected to the processing unit. The microchip is connected to the processing unit through the serial interface. The processing unit determines whether the network interface port is connected to the debugging host or connected to the external network, and selectively connects the network card or the serial interface to the network interface port according to the determination.