方法一（官方）：

Reachability

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框架地址：https://developer.apple.com/library/ios/samplecode/Reachability/Reachability.zip

使用方法

1>  添加一个联网状态监听对象

@property (nonatomic, strong) Reachability *reach;

2>  实例化监听对象

self.reach = [Reachability reachabilityWithHostName:@"www.baidu.com"];

3>  判断联网状态

- (void)netwrokStatusChanged {

    switch (self.reach.currentReachabilityStatus) {

        case NotReachable:

            SJLog(@"没有联网");

            break;

        case ReachableViaWiFi:

            SJLog(@"通过Wi-Fi上网");

            break;

        case ReachableViaWWAN:

            SJLog(@"通过3G上网");

            break;

        default:

            break;

    }

}

4>  利用通知中心实时监听联网状态

[[NSNotificationCenter defaultCenter] addObserver:selfselector:@selector(netwrokStatusChanged) name:kReachabilityChangedNotification object:nil];

[self.reach startNotifier];

- (void)dealloc {

    // 注册指定的通知监听

    [[NSNotificationCenter defaultCenter] removeObserver:selfname:kReachabilityChangedNotification object:nil];

}

iOS网络监测方法