On Jan 25, 2010, at 1:50 PM, Laurent Daudelin wrote:
What is the best way to detect that there is no internet connection from my Cocoa app?
SystemConfiguration.framework. It can even send you notifications in real-time as the network status changes.
Detecting no network would work too but I'd like to be able even if the Macintosh is connected to a network that it can't reach the internet. I know I could use a test connection but is there a better way?
A reasonable request, but the problem is that "reach the internet" is too vague a question. The main situation where it breaks down is on an intranet that requires use of a proxy to reach the outside world. In this case you are literally not connected to the Internet, even with a 1000baseT plug jacked into your computer, even though your web browser and email work fine.
If on the other hand you just mean "can I ping the router", this will be true on a home 802.11 network even when the DSL/cable modem is down, and there are no outside hosts reachable.
Basically you have to decide based on the specific functionality of your app. In a lot of cases what the app wants to know is "can I reach my server at foobar.com:12345?", and SystemConfiguration will let you ask that question. It won't be 100% accurate, though, because it gets its answer only from consulting the local routing tables, not from actually sending any packets.
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