sudo tcpdump -A -s 0 -i en4 host 10.28.2.207
mknetwork cache
[Reachability reachabilityWithHostname:self.hostName];
operation cancel
[self.reachability currentReachabilityStatus]
任何问题记得抓包
原文：http://www.cnblogs.com/javastart/p/4663316.html
