ios检查网络状态

+ (BOOL) connectedToNetwork {     // 创建零地址，0.0.0.0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;     // Get connect flags     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 = flag & kSCNetworkFlagsReachable;     BOOL needsConnection = flags & kSCNetworkFlagsConnectionRequired;       return (isReachable && !needsConnection) ? YES : NO; }