A desktop computer includes a host portion, a network interface card and a first interface. The network interface card includes a first pin, a second pin, and a third pin. The first interface includes a fourth pin connected to both the second and third pins of the network interface card, and a fifth pin connected to the first pin. The screen includes a second interface connected to the first interface, a first LED, and a second LED. The second interface includes a sixth pin connected to the fourth pin, and a seventh pin connected to the fifth pin. The seventh pin is connected to a power supply through the first LED. The sixth pin is connected to the power supply through the second LED. When there is communication through a network connection, the first LED and the fourth LED to flash synchronously.