+(BOOL) isNetworkEnabled

{

    BOOL bEnabled = FALSE;

    NSString *url = @"www.baidu.com";

    SCNetworkReachabilityRef ref =SCNetworkReachabilityCreateWithName(NULL, [urlUTF8String]);

    SCNetworkReachabilityFlags flags;

    bEnabled = SCNetworkReachabilityGetFlags(ref, &flags);

    CFRelease(ref);

    if (bEnabled) {

//        kSCNetworkReachabilityFlagsReachable：能够连接网络

//        kSCNetworkReachabilityFlagsConnectionRequired：能够连接网络，但是首先得建立连接过程

//        kSCNetworkReachabilityFlagsIsWWAN：判断是否通过蜂窝网覆盖的连接，比如EDGE，GPRS或者目前的3G.主要是区别通过WiFi的连接。

        BOOL flagsReachable = ((flags &kSCNetworkFlagsReachable) != 0);

        BOOL connectionRequired = ((flags &kSCNetworkFlagsConnectionRequired) != 0);

        BOOL nonWiFi = flags &kSCNetworkReachabilityFlagsTransientConnection;

        bEnabled = ((flagsReachable && !connectionRequired) || nonWiFi) ? YES : NO;

    }

    return bEnabled;

}

当作记录吧