问题
I am building an application and trying to check and see if a device is still available on the network (by connecting to the devices IPAddress). I am using reachability to confirm that it is available.
When I network access for the iOS device (turn on airplane mode for example) everything works properly, but if I remove the device from the network, reachability does not seem to notice the change.
It seems like reachability is caching the results, and not seeing the update.
回答1:
Don't use reachability then!
Use this bit of code instead which works a treat;
NSString *connected = [NSString stringWithContentsOfURL:[NSURL URLWithString:@"http://www.google.com"]];
wait(25000);
if (connected == NULL) {
NSLog(@"Not Connected");
//Code to show if not connected
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:nil message:@"Oops! You aren't connected to the Internet."
delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
[alert show];
[alert release];
} else {
NSLog(@"Connected Successfully!");
//Any other code for successful connection
}
回答2:
The SCReachability API only checks if the local hardware is configured such that it could reach the specified address; it does not actually attempt to reach it. To determine if the target is alive and kicking, you must attempt to open a connection to it.
回答3:
Check out this answer. While the pixelbit's answer is viable, burtlo is right to bring up that just waiting 25 seconds isn't a great idea. Using the NSURLConnection is much cleaner.
回答4:
Apple updated the Reachabilty class file. You can test it with latest Xcode. here is link: Apple Reachabilty Sample Code
I tested with Xcode 8.3.1 on iPhone 6 version 10.3.1. It will notify user for change in network status.
来源：https://stackoverflow.com/questions/7015644/ios-reachability-not-recognizing-when-host-is-removed