Getting notified when a VPN connection disconnects

How can I, within my Cocoa app, get a notification when the currently running VPN开发者_运维知识库 connection disconnects? I'm running Snow Leopard.

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You may be able to use the System Configuration framework for this. You can examine the System Configuration hierarchy with scutil(8), and you might have a look at HardwareGrowler's source code for examples of how to use the framework.

Also, documentation:

• http://developer.apple.com/mac/library/documentation/Networking/Conceptual/SystemConfigFrameworks/
• http://developer.apple.com/mac/library/documentation/Networking/Reference/SysConfig/