判断设备是否真正的连接互联网

• 手机连接了wifi，但是wifi没有连接网络
• 本地网络连接存在，但信号很差，实际无法连接到服务器
• wifi需要认证，我们虽然没有认证，但是已经连接了本地网络

苹果Reachability代码demo说明中也告诉了我们这个事实
"Reachability cannot tell your application if you can connect to a particular host, only that an interface is available that might allow a connection, and whether that interface is the WWAN."
大概意思就是：如果你连接到了一个特定的主机地址，Reachability不能告诉你的应用连接的接口是可用的，无论是一个连接，还是是wifi。（英语不好，见谅）
同样的经常用到的网络第三方库AFNetworking也是是能监测到本地网络的状态。感兴趣的可以自己写代码测试下。
我的测试代码如下

- (void)viewDidLoad {
    [super viewDidLoad];

    NSURL *URL = [NSURL 
    NSURLRequest *request = [NSURLRequest requestWithURL:URL];
    NSURLSession *session = [NSURLSession sharedSession];
    NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
        if (response == nil) {
            NSLog(@"没有网络");
        }
        else{
            NSLog(@"网络是通的");
        }
    }];
    
    [dataTask resume];

    [self checkNetwork];
    
}


- (BOOL)checkNetwork {
    __block BOOL result;
    AppDelegate *app = (AppDelegate *)[UIApplication sharedApplication].delegate;
    UIWindow *window = app.window;
    
    AFNetworkReachabilityManager *ReachabilityManager = [AFNetworkReachabilityManager sharedManager];
    [ReachabilityManager setReachabilityStatusChangeBlock:^(AFNetworkReachabilityStatus status) {
        MBProgressHUD *hud = [MBProgressHUD showHUDAddedTo:window animated:YES];
        result = status;
        switch (status) {
            case AFNetworkReachabilityStatusNotReachable:
                // 弹框提示的内容
                hud.labelText = @"当前网络不可用，请检查网络设置";
                break;
            case AFNetworkReachabilityStatusReachableViaWWAN:
                hud.labelText = @"2G/3G/4G";
                break;
            case AFNetworkReachabilityStatusReachableViaWiFi:
                hud.labelText = @"WiFi在线";
            default:
                break;
        }
        
        dispatch_async(dispatch_get_global_queue(0, 0), ^{
            // 显示时间1s
            sleep(5.);
            dispatch_async(dispatch_get_main_queue(), ^{
                // 让弹框消失
                [MBProgressHUD hideHUDForView:window animated:YES];
            });
        });
    }];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(networkStateChange) name:AFNetworkingReachabilityDidChangeNotification object:nil];
    [ReachabilityManager startMonitoring];
    return result;
}

- (void)networkStateChange{
    AFNetworkReachabilityManager *ReachabilityManager = [AFNetworkReachabilityManager sharedManager];
    //[ReachabilityManager startMonitoring];
    NSLog(@"manager.isReachable === %d++++++", ReachabilityManager.reachable);

}

针对这种情况，我的解决办法。虽然low点，笨点，关键是能用。

    // url地址最好写自己app要访问的地址，不能保证百度的服务器不抽筋，😄
    NSURL *URL = [NSURL 
    NSURLRequest *request = [NSURLRequest requestWithURL:URL];
    NSURLSession *session = [NSURLSession sharedSession];
    NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
        if (response == nil) {
            NSLog(@"没有网络");
        }
        else{
            NSLog(@"网络是通的");
        }
    }];
    
    [dataTask resume];