innernets

Example Use

- (void)applicationWillFinishLaunching:(NSNotification *)aNotification
{
  // check for future network connectivity changes
  [[NSNotificationCenter defaultCenter] addObserver:self
                                           selector:@selector(updateNetStatus:)
                                               name:kNetConnectionChangeNotification
                                             object:[NetConnection netConnection]];
}

- (void)updateNetStatus:(NSNotification *)notif
{
  if ([[NetConnection netConnection] isOnline]) {
    [[NSSound soundNamed:@"Ping"] play];
  } else {
    NSBeep();
  }
}

NetConnection.h

/**
 * NetConnection is a small class responsible for keeping track of when your
 * computer has access to the internet. It does so via the isOnline method
 * and posting notifications to the NSNotificiationCenter.
 *
 * @author leebyron lee@leebyron.com
 *
 *
 * To determine at any time if you are online
 *
 * BOOL live = [[NetConnection netConnection] isOnline];
 *
 *
 * To keep track of net connection change events, subscribe to the event via
 * the NSNotificationCenter:
 *
 * NSNotificationCenter* nc = [NSNotificationCenter defaultCenter];
 * [nc addObserver:self
 *        selector:@selector(netConnectionChanged:)
 *            name:kNetConnectionChangeNotification
 *          object:[NetConnection netConnection]];
 *
 * - (void)netConnectionChanged:(NSNotification*)notif {
 *   BOOL live = [[NetConnection netConnection] isOnline];
 * }
 *
 */

#import <Cocoa/Cocoa.h>
#import <Foundation/Foundation.h>
#import <SystemConfiguration/SystemConfiguration.h>
#import <ApplicationServices/ApplicationServices.h>

#define kNetConnectionChangeNotification @"NetConnectionChangeNotification"

@interface NetConnection : NSObject {
  SCDynamicStoreRef   dynamicStore;
  CFRunLoopSourceRef  runLoopSource;
  BOOL                isOnline;
  NSURL*              connectivityURL;
}

+ (NetConnection*)netConnection;
- (BOOL)isOnline;

@end

NetConnection.m

#import "NetConnection.h"

//---------------------------------------------------------------------------
@interface NetConnection (Private)

- (id)initWithURL:(NSURL*)url;
- (BOOL)isNetworkConnected;
- (void)changedKey:(NSString*)key userInfo:(NSDictionary*)userInfo;

@end

//---------------------------------------------------------------------------
void _NetConnectionNotificationCallback(
  SCDynamicStoreRef store,
  CFArrayRef changedKeys,
  void* source) {

  NSString* key;
  NSDictionary* info;
  NSEnumerator* keysE = [(NSArray *)changedKeys objectEnumerator];
  while (key = [keysE nextObject]) {
    info = (NSDictionary*)SCDynamicStoreCopyValue(store, (CFStringRef)key);
    [(NetConnection*)source changedKey:key userInfo:info];
    [info release];
  }
}

//---------------------------------------------------------------------------
@implementation NetConnection

static NetConnection* instance = nil;

+ (NetConnection*)netConnection
{
  if (instance == nil) {
    NSURL* url = [NSURL URLWithString:@"http://www.google.com/"];
    instance = [[NetConnection alloc] initWithURL:url];
  }
  return instance;
}

- (void)dealloc
{
  // remove dynamic store
  CFRunLoopRemoveSource(
    [[NSRunLoop currentRunLoop] getCFRunLoop],
    runLoopSource,
    kCFRunLoopCommonModes
  );
  CFRelease(runLoopSource);
  CFRelease(dynamicStore);

  [super dealloc];
}

- (BOOL)isOnline
{
  return isOnline;
}

@end

//---------------------------------------------------------------------------
@implementation NetConnection (Private)

- (id)initWithURL:(NSURL*)url
{
  self = [super init];
  if (self) {
    // check present connectivity
    connectivityURL = [url retain];
    isOnline = [self isNetworkConnected];
    
    // set up dynamic store
    SCDynamicStoreContext context = {0, (void *)self, NULL, NULL, NULL};
    dynamicStore = SCDynamicStoreCreate(
      NULL,
      (CFStringRef) [[NSBundle mainBundle] bundleIdentifier],
      _NetConnectionNotificationCallback,
      &context
    );
    
    // add dynamic store to run loop
    runLoopSource = SCDynamicStoreCreateRunLoopSource(NULL, dynamicStore, 0);
    CFRunLoopAddSource(
      [[NSRunLoop currentRunLoop] getCFRunLoop],
      runLoopSource,
      kCFRunLoopCommonModes
    );
    
    // only observe ip changes
    BOOL success = SCDynamicStoreSetNotificationKeys(
      dynamicStore,
      NULL,
      (CFArrayRef)[NSArray arrayWithObject:@"State:/Network/Global/IP.*"]
    );
    if (!success) {
      NSLog(@"Error: keys could not be observed.");
    }
  }
  return self;
}

- (BOOL)isNetworkConnected
{
  SCNetworkConnectionFlags status;
  BOOL success = SCNetworkCheckReachabilityByName(
    [[connectivityURL host] UTF8String],
    &status
  );

  success = success
            && (status & kSCNetworkFlagsReachable)
            && !(status & kSCNetworkFlagsConnectionRequired);

  return success;
}

- (void)changedKey:(NSString*)key userInfo:(NSDictionary*)userInfo
{
  BOOL wasOnline = isOnline;
  isOnline = userInfo != nil;
  if (wasOnline != isOnline) {
    NSNotificationCenter* nc = [NSNotificationCenter defaultCenter];
    [nc postNotificationName:kNetConnectionChangeNotification
                      object:self
                    userInfo:userInfo];
  }
}

@end