#import <Foundation/Foundation.h>
#import <SystemConfiguration/SystemConfiguration.h>
#import <netinet/in.h>typedef enum : NSInteger {NotReachable = 0,ReachableViaWiFi,ReachableViaWWAN
} NetworkStatus;extern NSString *kReachabilityChangedNotification;@interface Reachability : NSObject/*!* Use to check the reachability of a given host name.*/
+ (instancetype)reachabilityWithHostName:(NSString *)hostName;/*!* Use to check the reachability of a given IP address.*/
+ (instancetype)reachabilityWithAddress:(const struct sockaddr_in *)hostAddress;/*!* Checks whether the default route is available. Should be used by applications that do not connect to a particular host.*/
+ (instancetype)reachabilityForInternetConnection;/*!* Checks whether a local WiFi connection is available.*/
+ (instancetype)reachabilityForLocalWiFi;/*!* Start listening for reachability notifications on the current run loop.*/
- (BOOL)startNotifier;
- (void)stopNotifier;- (NetworkStatus)currentReachabilityStatus;/*!* WWAN may be available, but not active until a connection has been established. WiFi may require a connection for VPN on Demand.*/
- (BOOL)connectionRequired;@end

#import <arpa/inet.h>
#import <ifaddrs.h>
#import <netdb.h>
#import <sys/socket.h>#import <CoreFoundation/CoreFoundation.h>#import "Reachability.h"NSString *kReachabilityChangedNotification = @"kNetworkReachabilityChangedNotification";#pragma mark - Supporting functions#define kShouldPrintReachabilityFlags 1static void PrintReachabilityFlags(SCNetworkReachabilityFlags flags, const char* comment)
{
#if kShouldPrintReachabilityFlagsNSLog(@"Reachability Flag Status: %c%c %c%c%c%c%c%c%c %s\n",(flags & kSCNetworkReachabilityFlagsIsWWAN)                ? 'W' : '-',(flags & kSCNetworkReachabilityFlagsReachable)            ? 'R' : '-',(flags & kSCNetworkReachabilityFlagsTransientConnection)  ? 't' : '-',(flags & kSCNetworkReachabilityFlagsConnectionRequired)   ? 'c' : '-',(flags & kSCNetworkReachabilityFlagsConnectionOnTraffic)  ? 'C' : '-',(flags & kSCNetworkReachabilityFlagsInterventionRequired) ? 'i' : '-',(flags & kSCNetworkReachabilityFlagsConnectionOnDemand)   ? 'D' : '-',(flags & kSCNetworkReachabilityFlagsIsLocalAddress)       ? 'l' : '-',(flags & kSCNetworkReachabilityFlagsIsDirect)             ? 'd' : '-',comment);
#endif
}static void ReachabilityCallback(SCNetworkReachabilityRef target, SCNetworkReachabilityFlags flags, void* info)
{
#pragma unused (target, flags)NSCAssert(info != NULL, @"info was NULL in ReachabilityCallback");NSCAssert([(__bridge NSObject*) info isKindOfClass: [Reachability class]], @"info was wrong class in ReachabilityCallback");Reachability* noteObject = (__bridge Reachability *)info;// Post a notification to notify the client that the network reachability changed.[[NSNotificationCenter defaultCenter] postNotificationName: kReachabilityChangedNotification object: noteObject];
}#pragma mark - Reachability implementation@implementation Reachability
{BOOL _alwaysReturnLocalWiFiStatus; //default is NO
    SCNetworkReachabilityRef _reachabilityRef;
}+ (instancetype)reachabilityWithHostName:(NSString *)hostName
{Reachability* returnValue = NULL;SCNetworkReachabilityRef reachability = SCNetworkReachabilityCreateWithName(NULL, [hostName UTF8String]);if (reachability != NULL){returnValue= [[self alloc] init];if (returnValue != NULL){returnValue->_reachabilityRef = reachability;returnValue->_alwaysReturnLocalWiFiStatus = NO;}}return returnValue;
}+ (instancetype)reachabilityWithAddress:(const struct sockaddr_in *)hostAddress
{SCNetworkReachabilityRef reachability = SCNetworkReachabilityCreateWithAddress(kCFAllocatorDefault, (const struct sockaddr *)hostAddress);Reachability* returnValue = NULL;if (reachability != NULL){returnValue = [[self alloc] init];if (returnValue != NULL){returnValue->_reachabilityRef = reachability;returnValue->_alwaysReturnLocalWiFiStatus = NO;}}return returnValue;
}+ (instancetype)reachabilityForInternetConnection
{struct sockaddr_in zeroAddress;bzero(&zeroAddress, sizeof(zeroAddress));zeroAddress.sin_len = sizeof(zeroAddress);zeroAddress.sin_family = AF_INET;return [self reachabilityWithAddress:&zeroAddress];
}+ (instancetype)reachabilityForLocalWiFi
{struct sockaddr_in localWifiAddress;bzero(&localWifiAddress, sizeof(localWifiAddress));localWifiAddress.sin_len = sizeof(localWifiAddress);localWifiAddress.sin_family = AF_INET;// IN_LINKLOCALNETNUM is defined in <netinet/in.h> as 169.254.0.0.localWifiAddress.sin_addr.s_addr = htonl(IN_LINKLOCALNETNUM);Reachability* returnValue = [self reachabilityWithAddress: &localWifiAddress];if (returnValue != NULL){returnValue->_alwaysReturnLocalWiFiStatus = YES;}return returnValue;
}#pragma mark - Start and stop notifier- (BOOL)startNotifier
{BOOL returnValue = NO;SCNetworkReachabilityContext context = {0, (__bridge void *)(self), NULL, NULL, NULL};if (SCNetworkReachabilitySetCallback(_reachabilityRef, ReachabilityCallback, &context)){if (SCNetworkReachabilityScheduleWithRunLoop(_reachabilityRef, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode)){returnValue = YES;}}return returnValue;
}- (void)stopNotifier
{if (_reachabilityRef != NULL){SCNetworkReachabilityUnscheduleFromRunLoop(_reachabilityRef, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode);}
}- (void)dealloc
{[self stopNotifier];if (_reachabilityRef != NULL){CFRelease(_reachabilityRef);}
}#pragma mark - Network Flag Handling- (NetworkStatus)localWiFiStatusForFlags:(SCNetworkReachabilityFlags)flags
{PrintReachabilityFlags(flags, "localWiFiStatusForFlags");NetworkStatus returnValue = NotReachable;if ((flags & kSCNetworkReachabilityFlagsReachable) && (flags & kSCNetworkReachabilityFlagsIsDirect)){returnValue = ReachableViaWiFi;}return returnValue;
}- (NetworkStatus)networkStatusForFlags:(SCNetworkReachabilityFlags)flags
{PrintReachabilityFlags(flags, "networkStatusForFlags");if ((flags & kSCNetworkReachabilityFlagsReachable) == 0){// The target host is not reachable.return NotReachable;}NetworkStatus returnValue = NotReachable;if ((flags & kSCNetworkReachabilityFlagsConnectionRequired) == 0){/*If the target host is reachable and no connection is required then we'll assume (for now) that you're on Wi-Fi...*/returnValue = ReachableViaWiFi;}if ((((flags & kSCNetworkReachabilityFlagsConnectionOnDemand ) != 0) ||(flags & kSCNetworkReachabilityFlagsConnectionOnTraffic) != 0)){/*... and the connection is on-demand (or on-traffic) if the calling application is using the CFSocketStream or higher APIs...*/if ((flags & kSCNetworkReachabilityFlagsInterventionRequired) == 0){/*... and no [user] intervention is needed...*/returnValue = ReachableViaWiFi;}}if ((flags & kSCNetworkReachabilityFlagsIsWWAN) == kSCNetworkReachabilityFlagsIsWWAN){/*... but WWAN connections are OK if the calling application is using the CFNetwork APIs.*/returnValue = ReachableViaWWAN;}return returnValue;
}- (BOOL)connectionRequired
{NSAssert(_reachabilityRef != NULL, @"connectionRequired called with NULL reachabilityRef");SCNetworkReachabilityFlags flags;if (SCNetworkReachabilityGetFlags(_reachabilityRef, &flags)){return (flags & kSCNetworkReachabilityFlagsConnectionRequired);}return NO;
}- (NetworkStatus)currentReachabilityStatus
{NSAssert(_reachabilityRef != NULL, @"currentNetworkStatus called with NULL SCNetworkReachabilityRef");NetworkStatus returnValue = NotReachable;SCNetworkReachabilityFlags flags;if (SCNetworkReachabilityGetFlags(_reachabilityRef, &flags)){if (_alwaysReturnLocalWiFiStatus){returnValue = [self localWiFiStatusForFlags:flags];}else{returnValue = [self networkStatusForFlags:flags];}}return returnValue;
}@end

// 开启网络状况的监听
    [[NSNotificationCenter defaultCenter] addObserver:selfselector:@selector(reachabilityChanged:)name:kReachabilityChangedNotificationobject:nil];self.reachability = [Reachability reachabilityWithHostName:@"www.baidu.com"];[self.reachability startNotifier];

- (void)reachabilityChanged:(NSNotification* )note
{Reachability *curReach  = [note object];NetworkStatus status    = [curReach currentReachabilityStatus];NSLog(@"网络状态值: %ld", (long)status);// 根据网络状态值，在这里做你想做的事// ...
}