检测网络是否有效

//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;
}