iOS实现实时检测网络状态的示例代码

#import <foundation/foundation.h> 
#import <systemconfiguration/systemconfiguration.h> 
#import <netinet/in.h> 
 
//http://www.cnblogs.com/xiaofeixiang 
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 1 
static void printreachabilityflags(scnetworkreachabilityflags flags, const char* comment) 
{ 
#if kshouldprintreachabilityflags 
 nslog(@"reachability flag status: %c%c %c%c%c%c%c%c%c %s\n", 
  //当前网络2g/3g/4g蜂窝网络 
  (flags & kscnetworkreachabilityflagsiswwan)    ? 'w' : '-', 
  //网络是否可达 
  (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"); 
 //http://www.cnblogs.com/xiaofeixiang 
 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; 
} 
//通过域名进行实例化 博客园-fly_elephant 
+ (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; 
} 
//通过ip地址实例化reachability 
+ (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; 
} 
//检测是否能够直接连上互联网 
+ (instancetype)reachabilityforinternetconnection 
{ 
 struct sockaddr_in zeroaddress; 
 bzero(&zeroaddress, sizeof(zeroaddress)); 
 zeroaddress.sin_len = sizeof(zeroaddress); 
 zeroaddress.sin_family = af_inet; 
 return [self reachabilitywithaddress:&zeroaddress]; 
} 
//检测当前网络是否能够联上wifi 
+ (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 voidvoid *)(self), null, null, null}; 
 //scnetworkreachabilitysetcallback函数为指定一个target 
 //当设备对于这个target链接状态发生改变时(比如断开链接，或者重新连上)，则回调reachabilitycallback函数， 
 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; 
} 
//获取当前网络状态 
- (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

- (bool)application:(uiapplication *)application didfinishlaunchingwithoptions:(nsdictionary *)launchoptions { 
 //添加一个系统通知 
 [[nsnotificationcenter defaultcenter] addobserver:self selector:@selector(reachabilitychanged:) name:kreachabilitychangednotification object:nil]; 
 //初始化 
 self.internetreachability=[reachability reachabilityforinternetconnection]; 
 //通知添加到run loop 
 [self.internetreachability startnotifier]; 
 [self updateinterfacewithreachability:_internetreachability]; 
 return yes; 
} 

(void) reachabilitychanged:(nsnotification *)note 
{ 
 reachability* curreach = [note object]; 
 nsparameterassert([curreach iskindofclass:[reachability class]]); 
 [self updateinterfacewithreachability:curreach]; 
} 
- (void)updateinterfacewithreachability:(reachability *)reachability 
{ 
 networkstatus netstatus = [reachability currentreachabilitystatus]; 
 switch (netstatus) { 
 case notreachable: 
  nslog(@"====当前网络状态不可达=======http://www.cnblogs.com/xiaofeixiang"); 
  break; 
 case reachableviawifi: 
  nslog(@"====当前网络状态为wifi=======博客园-fly_elephant"); 
  break; 
 case reachableviawwan: 
  nslog(@"====当前网络状态为3g=======keso"); 
  break; 
 } 
}