//检测网络是否有效- (BOOL) checkNetworkIsValid {    struct sockaddr_in zeroAddress;    bzero(&zeroAddress, sizeof(zeroAddress));    zeroAddress.sin_len = sizeof(zeroAddress);    zeroAddress.sin_family = AF_INET;            SCNetworkReachabilityRef defaultRouteReachability = SCNetworkReachabilityCreateWithAddress(NULL, (struct sockaddr *)&zeroAddress);    SCNetworkReachabilityFlags flags;        BOOL didRetrieveFlags = SCNetworkReachabilityGetFlags(defaultRouteReachability, &flags);    CFRelease(defaultRouteReachability);        if (!didRetrieveFlags) {        return NO;    }        BOOL isReachable = flags & kSCNetworkFlagsReachable;    BOOL needsConnection = flags & kSCNetworkFlagsConnectionRequired;    // = flags & kSCNetworkReachabilityFlagsIsWWAN;    BOOL nonWifi = flags & kSCNetworkReachabilityFlagsTransientConnection;    BOOL moveNet = flags & kSCNetworkReachabilityFlagsIsWWAN;        return ((isReachable && !needsConnection) || nonWifi || moveNet) ? YES : NO;}

#import "CheckNetwork.h"#import <netinet/in.h>#import <SystemConfiguration/SCNetworkReachability.h>@implementation CheckNetwork+ (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;    BOOL isWWAN = flags & kSCNetworkReachabilityFlagsIsWWAN;    return (isReachable && (!needsConnection || isWWAN)) ? YES : NO;}