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Windows XP : how to check which port has been opened for a particular PC?

Posted on 2009-05-10
Medium Priority
Last Modified: 2012-05-06

Since I just relocated to another office and hence the IP address of my PC need to change to another one due to network setting issues.  Yet, after I used the new IP address, I found that I can not access to my applications due to port not open.

In our company, the default is block all ports while when necessary, we need to apply for port opening for a particular application/access.  And we have quite a lot of firewalls as well (around one firewall per switch).  Since it is nearly impossible for our firewall admin to look at each firewall and sort out from each of it and find out whether I have opened which port for which server.

Therefore, I would like to ask whether there is a tool or way to sort it out for me and transfer all opened ports in my old IP address to the new one.  I can ask my colleague to setup a PC which using my old IP address in the old office but it is impossible to ask them to open all applications that need to open firewall port and validate the connections.

Kindly please help.

Question by:StanleyLMW
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Expert Comment

ID: 24351259
I need more information. Do you know what ports you need opened? Do you know what ports were open on your old computer? An IT staff should know their firewalls, and how to open ports, are you sure they are not blowing you off? What firewall are you talking about, the network firewall, or a software firewall on your computer? Please provide more information about the infrastructure of  your problem.

Expert Comment

ID: 24351275
Hi Stanley, You will not be able to transfer your old port settings to your new location unless the routers are identical, but you can run a tool that will tell you which ports your programs are trying to use. Open the program you want to see the ports for.

Open a command prompt by going to Start, Run, and typing cmd then hit ok.
When the black window opens, type in netstat -a and then hit enter.

This will list all the Ip's and port numbers that are in use. You should be able
to tell which ip your program is trying to get to, and which port it is using to get out of the gateway.

If you need somthing even more descriptive, you can use TCPview
I hope this helps

-Scott E

Author Comment

ID: 24351532
Hi Technious,
For sure I have no complete pictures on what ports had been opened for my old computer or I just use the list and just re-apply for port opening will do.  I'm not sure whether our network firewall admin (not software firewall) do blow me off or not but they just told me that it is quite impossible for him to scan through all network firewalls for the existence of my old IP address.
Hi Scottyvanman,
Thanks for your suggestion, I have just test it but seems that it only report the port opened while the application/connection are in use but not for connections other than that.  Though it contains an option of showing all those unconnected endpoints but still can not show some connections that I know that it should have the port already been opened. (e.g.  I can get access to a remote server by mapping a share drive of it, but now it can not be, sure related to firewall issue but even I use the tool, it still can not show an entry with the IP address of the remote server that I had just mentioned).  Is it mean that it is impossible to do that ?
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Expert Comment

ID: 24351588
it should be showing you the IP address that you are trying to get to, but I was of the inderstandng that you were trying to get the port numbers. What is it you are after here?

Expert Comment

ID: 24352419
Hi Stanley,

I'd suggest you to take this approach:
1. Identify exactelly what applications you need to use (Accounting software, internet file sharing, messanger software, etc) and take it one step at the time.
2. Take applications one by one, and check the error you get when trying to access it. It might be other issues than the firewall.
3. Check the documentation for your applications to see what ports it needs. For example, if you are using some accounting software that needs access to outside servers, read the documentation and/or contact their technical support to find out needed ports.
4. Ask the firewall admin to grant you access to those ports, and test each step carefully.

By doing wild guesses you will only loose time and have no result.
LVL 10

Accepted Solution

Kechka earned 1000 total points
ID: 24352699
Try port scanner from to find out all open ports on computer.

Assisted Solution

sfarazmand earned 1000 total points
ID: 24357063
You will need to find out what Firewall your old IP was attached to. Once there those settings can be easily found, then they can be recreated or transferred to the firewall managing your current location.

You can use Active Ports ( CurrPorts ( to check what ports are open, and what apps are using them.  I would download one and run the app then check what port it's using. Additionally, some apps use different ports for the different tasks they perform. So the easiest way to be sure you have all the settings is by finding the exceptions on the firewall.

Expert Comment

ID: 24359468
I am still having trouble understanding what you are looking for. Do you need the applications to communicate with the internet, or do you need the internet to communicate with your applications. It is difficult to say what ports your old IP have opened unless you have access to that Computer and it still has the same IP. I am with MariusSunchaser on this, you need to figure out what applications you need and in what way they need to communicate with the Internet, and then make the requests with the administrator.

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