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On my Mac, I'm having trouble with a UDP port (500) that is "already in use", but it doesn't have an associated process anymore.

sudo netstat -na | grep "udp4.*\.500\>"


udp4       0      0     *.*                               
udp4       0      0     *.*                               

But lsof doesn't show a process on port 500 (ie "sudo lsof -i:500 -P" reports nothing).

Note that I am using "sudo" for these calls, so it should show all resources.

How can I figure out how to unbind the resource attached to port 500 so I can use it again?

share|improve this question
And if you try sudo lsof -i@ -P and sudo lsof -i@ -P? – jaume Nov 12 '12 at 8:06
@Jaume, blank result, while netstat still shows the ports. This is driving me nuts, it's making my vpn client not work. – Chocohound Nov 12 '12 at 14:54

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