类似于一个网络状况的探针。

　　[[NSNotificationCenter defaultCenter] addObserver: self selector: @selector(reachabilityChanged:) name: kReachabilityChangedNotification object: nil];

    hostReach = [[Reachability reachabilityWithHostName: @"hubj.cnblogs.com"] retain];

    [hostReach startNotifier];

    wifiReach=[[Reachability reachabilityForLocalWiFi]retain];

    [wifiReach startNotifier];

- (void)reachabilityChanged: (NSNotification* )note {

    Reachability* curReach = [note object];

    NSParameterAssert([curReach isKindOfClass: [Reachability class]]);

    NetworkStatus netStatus = [curReach currentReachabilityStatus];

    switch (netStatus)

    {

        case NotReachable:

        {

            NSLog(@"Access Not Available");

            break;

        }

        case ReachableViaWWAN:

        {

            NSLog(@"Reachable WWAN");

            break;

        }

        case ReachableViaWiFi:

        {

            NSLog(@"Reachable WiFi");

            break;

        }

    }

}

判断网络是否连接

/***

* 此函数用来判断是否网络连接服务器正常

* 需要导入Reachability类

*/

+ (BOOL)isExistenceNetwork

{

    BOOL isExistenceNetwork;

    Reachability *reachability = [Reachability reachabilityWithHostName:@""];  // 测试服务器状态

     switch([reachability currentReachabilityStatus]) {

            case NotReachable:

                  isExistenceNetwork = FALSE;

                  break;

             case ReachableViaWWAN:

                   isExistenceNetwork = TRUE;

                   break;

              case ReachableViaWiFi:

                    isExistenceNetwork = TRUE;

                    break;

     }

     return  isExistenceNetwork;

}

实时通知网络状况

/*

* 在应用委托的方法didFinishLaunchingWithOptions中添加

*/

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(reachabilityChanged:) name:kReachabilityChangedNotification object:nil];

reachability = [[Reachability reachabilityWithHostName:@"www.baidu.com"] retain];

[reachability startNotifier];

........

return YES;

/**

*此函数通过判断联网方式，通知给用户

*/

- (void)reachabilityChanged:(NSNotification *)notification

{

      Reachability *curReachability = [notification object];

      NSParameterAssert([curReachability isKindOfClass:[Reachability class]]);

      NetworkStatus curStatus = [curReachability currentReachabilityStatus];

      if(curStatus == NotReachable) {

          [DOIN_Util logFax:@"连接失败"];

      }

}