在一个网段内，如果网卡被设置为混合模式，当网络中有数据报传输时，无论数据报是否属于本机，网卡都会接收到该数据报。利用这点实现一个网络监听工具。-In a network segment, if the card is set to mixed mode, when the network has datagram transmission, regardless of whether the data reported in this machine, card will be received