checking network reachability in real time

Question

When the user presses a button, I need to know whether the device is connected to the internet at that very instant--not whether he was connected 3 seconds ago. The reachability (tonymillion) notifier takes about that long to update after there is a change in network reachability.

I thought that I would be able to check for actual access in real time using the following methods:

if (!([[Reachability reachabilityWithHostname:@"www.google.com"] currentReachabilityStatus] == NotReachable)) NSLog(@"reachable");
if ([[Reachability reachabilityWithHostname:@"www.google.com"] currentReachabilityStatus] == NotReachable) NSLog(@"not reachable");

But results indicated that in fact currentReachabilityStatus does not check for internet access; it only checks the same flag that is updated with ~3 seconds' delay.

What's an efficient way of actually checking for network access on the spot?

Answer 1

As you wished in the comments above here is a solution using a "HEAD" request.

1. Make your class conforming to the NSURLConnectionDelegate.
2. Implement the connection:didReceiveResponse: delegate method
3. Optionally implement the connection:didFailWithError: delegate method

So your setup could look like this:

YourClass.m

@interface YourClass () <NSURLConnectionDelegate>
@property (strong, nonatomic) NSURLConnection *headerConnection;
@end

@implementation YourClass

- (void)viewDidLoad {
    // You can do this in whatever method you want
    NSMutableURLRequest *headerRequest = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:@"http://www.google.com"] cachePolicy:NSURLRequestReloadIgnoringLocalAndRemoteCacheData timeoutInterval:10.0];
    headerRequest.HTTPMethod = @"HEAD";
    self.headerConnection = [[NSURLConnection alloc] initWithRequest:headerRequest delegate:self];
}

#pragma mark - NSURLConnectionDelegate Methods

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
    if (connection == self.headerConnection) {
        // Handle the case that you have Internet; if you receive a response you are definitely connected to the Internet
    }
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
    // Note: Check the error using `error.localizedDescription` for getting the reason of failing
    NSLog(@"Failed: %@", error.localizedDescription);
}