networking - How can one verify the port configuration of a firewall?

06
2014-04
  • mobibob

    I am a contractor on a project and have provided a port configuration requirement to the Server Hosting service provider for my project. How can I verify that the ports are configured and "open" for me to complete my server-app install?

    Since I do not yet have a working server, is it possible to test ports without a listener?

    Are there tools available to be the listener? -- I have Network Utility on Mac to be the port scanner.

    I need this before I can approve the work is complete, and I don't want to have to go back and ask for more changes resulting from an incomplete test.

    • Answers
  • Robert

    Take a look at netcat. A little console tool that perfectly suits your needs. You can create sender and listener with a short one-liner, this is perfect for testing ports.


    • Related Question

    networking - Is there a simple way to detect ISP port blocking?
  • Will M

    Is there a way to tell the difference between my ISP blocking traffic on certain ports and my NAT router/firewall blocking that traffic? The sites “Shields Up” and “Can you see me” show my ports closed or not accessible, but I assume that is primarily due to the NAT router. (Obviously, I could just remove the router, connect directly and use those sites, but is there a simple way to test without doing that?)


    • Related Answers
  • Joey

    You can set your computer as the DMZ in the router configuration, which means that NAT essentially passes everything to you.

  • Firebinder

    Firebind.com is able to tell you whether any of the 65535 UDP or TCP ports are being blocked between your client machine and the Internet. They have a Java Applet client that sends packets back and forth from your machine to their server over the port(s) of your choosing, and if the packets transfer successfully, you know the port isn't blocked by any intervening firewall (such as your own home router or your ISPs firewall.)

    So in your case you could first run tests from behind your router and get a list of all blocked ports. Then you could connect your machine directly to the Internet (bypassing the firewall) and run the tests again. By comparing the results you'd be able to figure out the difference between what your home router blocks and what your ISP blocks.

    It's important to note that Firebind is NOT a port scanner. It's a "PATH" scanner.

    http://www.firebind.com

  • JP Alioto

    You could set your router/firewall to do logging and see what it is blocking specifically.