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I've got an application that used to work perfectly with all outgoing ports open and all incoming ports closed. Now we've closed all outgoing ports except a few specific ones e.g. http and it's not working any more. Is there a way I can find out using tools like wireshark which outgoing request is getting blocked so I can tell my sysadmin what to open?

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I should mention I tried looking at vendor documentation, etc. – configurator Jan 24 '11 at 20:45
Have you tried contacting the vendor's support to ask which ports are used? – jscott Jan 24 '11 at 20:47
Have you tried using netstat to show you which ports? – John Gardeniers Jan 24 '11 at 23:42

It should be listed in your firewall's log. If you don't log blocked outgoing traffic, turn this on at least until you know what to open.

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+1, Wireshark will also show TCP SYN packets trying to open the connection and should have the destination port listed there too. – Chris S Jan 24 '11 at 20:52

Use this app and it will list out all the connections/ports/addresses that any app running is using.

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