iOS 判断网络有无

- (BOOL)CheckNetWork{

struct sockaddr zeroAddress;
bzero(&zeroAddress, sizeof(zeroAddress));
zeroAddress.sa_len = sizeof(zeroAddress);
zeroAddress.sa_family = AF_INET;
SCNetworkReachabilityRef defaultRouteReachability =
SCNetworkReachabilityCreateWithAddress(NULL, (struct sockaddr *)&zeroAddress);
SCNetworkReachabilityFlags flags;
BOOL didRetrieveFlags =
SCNetworkReachabilityGetFlags(defaultRouteReachability, &flags);
CFRelease(defaultRouteReachability);
if (!didRetrieveFlags) {
    printf("Error. Count not recover network reachability flags\n");
    return NO;
}
BOOL isReachable = flags & kSCNetworkFlagsReachable;
BOOL needsConnection = flags & kSCNetworkFlagsConnectionRequired;
BOOL isNetworkEnable  =(isReachable && !needsConnection) ? YES : NO;
dispatch_async(dispatch_get_main_queue(), ^{
    [UIApplication sharedApplication].networkActivityIndicatorVisible =isNetworkEnable;/*  网络指示器的状态： 有网络 ： 开  没有网络： 关  */
});
return isNetworkEnable;
}