Windows – How to tell what outbound ports are blocked (Windows 2003)

portswindows-server-2003

I'm trying to troubleshoot a custom application that lives inside of a firewall on an enterprise network running Windows 2003 server. Our application uses PHP/cURL to send XML data to a publicly hosted website. By default, one can't uses a browser on this server; however, an earlier iteration of the application was able to go outbound on port 80 (in spite of the browser lock down).

I need a simple way of determining whether I can reach a particular destination via port 80 or port 443 (e.g. http://www.foo.com/other/import-xml?md87t9=g456342135kj5f7)

I would like to verify this before I work with the customer on changing their firewall/web filtering setup.

Best Answer

You need a system at that address running a service on that port, and that system needs to not have incoming traffic blocked. If that is true, then you need to try to communicate somehow on that port to the service listening. That is the only 100% reliable way to know for sure without knowing the exact firewall configuration on both sides.

However, if the only problem you are having is that you can't use a browser, and you are trying to test from Windows Server 2003, you can issue a manual HTTP request using telnet. Try this in a command prompt:

telnet yourserver.com 80

Then, press ENTER once, and then type exactly (you won't be able to see what you type):

GET / HTTP/1.1

Then press ENTER.

If a webserver is listening on that port and is reachable, you'll get a bunch of HTML back. If not, the connection will time out.

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