实时判断网络连接状态

+ (BOOL) connectedToNetwork{

//创建零地址，0.0.0.0的地址表示查询本机的网络连接状态

struct sockaddr_in zeroAddress;

bzero(&zeroAddress, sizeof(zeroAddress));

zeroAddress.sin_len = sizeof(zeroAddress);

zeroAddress.sin_family = AF_INET;

// Recover reachability flags

SCNetworkReachabilityRef defaultRouteReachability = SCNetworkReachabilityCreateWithAddress(NULL, (struct sockaddr *)&zeroAddress);

SCNetworkReachabilityFlags flags;

//获得连接的标志

BOOL didRetrieveFlags = SCNetworkReachabilityGetFlags(defaultRouteReachability, &flags);

CFRelease(defaultRouteReachability);

//如果不能获取连接标志，则不能连接网络，直接返回

if (!didRetrieveFlags){

return NO;

}

//根据获得的连接标志进行判断

BOOL isReachable = flags & kSCNetworkFlagsReachable;

BOOL needsConnection = flags & kSCNetworkFlagsConnectionRequired;

return (isReachable && !needsConnection) ? YES : NO;

}