Reachability.m

/*
     File: Reachability.m
 Abstract: Basic demonstration of how to use the SystemConfiguration Reachablity APIs.
  Version: 3.0
 
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 */

#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 %s\n",
          (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 localWiFiRef;
	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->localWiFiRef = 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->localWiFiRef = 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->localWiFiRef = 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");
	BOOL 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;
	}

	BOOL 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;
        }
    }
    
	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 reachabilityRef");
	NetworkStatus returnValue = NotReachable;
	SCNetworkReachabilityFlags flags;
    
	if (SCNetworkReachabilityGetFlags(reachabilityRef, &flags))
	{
		if (localWiFiRef)
		{
			returnValue = [self localWiFiStatusForFlags:flags];
		}
		else
		{
			returnValue = [self networkStatusForFlags:flags];
		}
	}
    
	return returnValue;
}


@end