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How can I quickly find listening/open ports on my computer ?

You can use the NETSTAT command to quickly see all the used and listening ports on your computer. Note it is not a complete substitute for a port scanning tool. If you'd like to have your computer remotely scanned for open ports use our Security Scan instead.

To see a list of listening ports, open Command Prompt and type:

C:\> netstat -an |find /i "listening"

You can change "listening" to "established" to see what ports your computer actually communicates with.


In Windows XP and Win2k3 Server you can use the -O switch with the NETSTAT command to also get a list of all the owning process ID associated with each connection:

C:\> netstat -ao |find /i "listening"

To see all open, closing, established and listening ports, simply use:

C:\> netstat -a (or netstat -ao in XP/Win2k3)

You can also make the netstat command refresh periodically by adding a number of seconds at the end, for example, to make it refresh every 5 seconds, use something like:

C:\> netstat -an 5


Notes:
The netstat command has a number of other useful command line parameters, you can see short description of all of them using: netstat /?
Also, you might want to perform an outside port scan to see what ports are accepting connections according to an external machine. See: SG Security Scan
You can see process identifiers using the following command at the command prompt: tasklist and tasklist /svc


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by anonymous - 2013.01.10 15:28
Thank you for this. However I have another problem. I have 6 computers daisy chained together to create a render farm. Two of my computers "cannot connect to server, because target machine actively refused connection." How can I get my main computer and the other 5 to "speak" to eachother? Would my computer and the other 5 be listening on the same port?

Also, on the main computer and the other 5, the same TCP ports are listening.

Thank you,
by Philip - 2013.01.14 13:00
"Actively refused connection" sounds like either a closed port, or firewall issue. You'd also have to make sure the necessary services are running on both computers to be able to establish the connection. I am not familiar with your OS/setup to offer more specific info.
by newSocrates - 2013.04.09 21:22
Hello, could you most kindly help me with port unavailable problem I have been having since I moved to Rogers (my new ISP). I have configured port forwarding in my gateway (Cisco DPC3825), and made exceptions in windows firewall for port 13000, but all the existing programs for open port checking say that it is not available. Today, I have found a cisco tools (https://supportforums.cisco.com/docs/DOC-10272), and followed its instructions, which showed that the port status is stealth, which according to Cisco is evidence for the ISP is blocking the port. So, I talked to the technical service of my ISP, and the supervisor assured me that port 13000 is not blocked either for TCP or UDP. And yet, this port is still not available for the particular program (freephoneline.ca) I am using it for. I have just followed your advice above to use netstat -a, but it does not list port 13000. Perhaps I have not done things right in my windows firewall, but at this point, I have no idea how to go about it. If you like I could send you all the test results I have made so far. I would very much like to have port 13000 working. Could you kindly help me with this?
by anonymous - 2013.12.11 10:43
how to ports is open or not
by Philip - 2014.01.13 11:39
A port in "stealth" mode simply means it is not responding, i.e. it does not report back that it is closed/open. It is the normal state for most ports behind a NAT router. It does not necessarily mean that your ISP is blocking it.

I'd suggest trying to open another port, and check whether it is open with our security scan. If it remains in the same "stealth" state, there is an issue with your port forwarding locally, rather than your ISP.

Please also note you may be able to get answers much quicker on our forums, rather than the comments section.
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