I followed this link iPhone reachability checking but can anyone help me with if the user has not connected to internet how to take him to setting menu
In iOS 5.0 and 5.0.1 you can use this:
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"prefs://"]];
However, in iOS 4.3 and older and in iOS 5.1 and later, this URL scheme is not associated with the Settings app - if you want your app to be accepted in the AppStore, you don't really have any option other than asking the user to go to Settings. However, if jailbroken/non-AppStore development is an alternative, you can use a private function for opening an app:
SBSLaunchApplicationWithIdentifier(CFSTR("com.apple.preferences"), false);
This function is located in the SpringBoardServices private framework.