说明：  PING程序设计和实现，系统自带的ping命令当它接送完所有ICMP报文后，会对所有发送和所有接收的ICMP报文进行统计，从而计算ICMP报文丢失的比率。为达此目的，定义两个全局变量：接收计数器和发送计数器，用于记录ICMP报文接受和发送数目。丢失数目=发送总数-接收总数，丢失比率=丢失数目/发送总数
(PING program design and realization, the system comes with the ping command when it transfer all the ICMP packet will have all senders and all receivers of the ICMP packet statistics in order to estimate the ICMP packet loss ratio. To this end, define two global variables: the receiving and sending counter counter, used to record the ICMP packet and send the number of accepted. Number lost = sent total- to receive the total number of loss ratio = loss/Send the total number of)