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The port 80 on one of our servers is locked by some process. Using netstat command we found that the port 80 is being used by process with ID 4(System). No clue on what exe or service is using this port.

Our IIS is down because of this. How to identify and kill the process that blocked port 80 (windows 2003 OS)?

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migrated from Oct 11 '09 at 17:13

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Really belongs on It's not Skype is it? – spender Oct 8 '09 at 9:32
have you tried using the tools from to determine the process? e.g. TCPView – Bob Oct 8 '09 at 9:38
The best tool for that by Sysinternals is Process Explorer. 1up for bobs comment. – Koekiebox Oct 8 '09 at 9:55
up vote 1 down vote accepted

I get this all the time with Skype. Kill Skype + process then try restarting IIS.

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+1 for Skype comment. See it all the time even though Skype shouldn't be running on the IIS server in my opinion. – KPWINC Oct 11 '09 at 17:25

You can turn off Skype's port 80 listening service by going to Options->Advanced->Connection and unchecking "Use port 80 and 443 as alternatives for incoming connections."

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