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    <p>The Reachability class and <code>-reachabilityWithHostname:</code> is designed to be a quick, fail-fast mechanism to determine whether you have basic network connectivity to the host. If you need to verify that a particular URL can be downloaded, you need to be looking at using <code>NSURLConnection</code> to retrieve the contents of the URL in order to verify that it is truly available.</p> <p>Depending on whether you need to do this in the foreground or background, you can either use the simple-but-blocking:</p> <pre><code>+ (NSData *)sendSynchronousRequest:(NSURLRequest *)request returningResponse:(NSURLResponse **)response error:(NSError **)error </code></pre> <p>or you can use the more complicated method of creating an NSURLConnection object, setting up a delegate to receive responses and wait for those responses to come in.</p> <p>For the simple case:</p> <pre><code> NSURL *myURL = [NSURL URLWithString: @"http://example.com/service.asmx"]; NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL: myURL]; [request setHTTPMethod: @"HEAD"]; NSURLResponse *response; NSError *error; NSData *myData = [NSURLConnection sendSynchronousRequest: request returningResponse: &amp;response error: &amp;error]; </code></pre> <p>If you receive back a non-nil myData, you've got some kind of connectivity. <code>response</code> and <code>error</code> will tell you what the server responded to you (in the case of response and if you received a non-nil myData) or what kind of error occurred, in the case of a nil myData.</p> <p>For the non-trivial case, you can get good guidance from Apple's <a href="https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/URLLoadingSystem/Tasks/UsingNSURLConnection.html" rel="noreferrer">Using NSURLConnection</a>.</p> <p>If you don't want to stall your foreground process, you can do this two different ways. The above documentation will provide information on how to implement the delegate, etc. However, a simpler implementation would be to use GCD to send the Synchronous request on a background thread, and then message yourself on the main thread when you are done.</p> <p>Something like this:</p> <pre><code> NSURL *myURL = [NSURL URLWithString: @"http://example.com/service.asmx"]; NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL: myURL]; [request setHTTPMethod: @"HEAD"]; dispatch_async( dispatch_get_global_queue( DISPATCH_QUEUE_PRIORITY_BACKGROUND, NULL), ^{ NSURLResponse *response; NSError *error; NSData *myData = [NSURLConnection sendSynchronousRequest: request returningResponse: &amp;response error: &amp;error]; BOOL reachable; if (myData) { // we are probably reachable, check the response reachable=YES; } else { // we are probably not reachable, check the error: reachable=NO; } // now call ourselves back on the main thread dispatch_async( dispatch_get_main_queue(), ^{ [self setReachability: reachable]; }); }); </code></pre>
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    1. POchecking reachability against a specific page in a URL
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    1. COcan you provide a simple example of how to do it in the background to prevent hanging of the application ?
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    2. COI've added an example of using GCD to make the synchronous request on an asynchronous call to the background thread, returning the response back to your main thread as a message when it completes. Hope that helps.
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    3. COawesome! there is a small mistake in the above code, you have to set reachable = YES in the first if statement and to NO in the second if statement. thank you so much gaige.
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