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How-to Scan for Ports on Your Network

Scan for Ports

How-to Scan for Ports

Recently I was working at a customer site attempting to troubleshoot file synchronization (DFS) between two file servers at remote locations. DFS stands for Distributed File System which is a Microsoft technology that allows two file servers to appear as one. After 15 minutes of the DFS service running the service would stop. I had been implementing various troubleshooting techniques to resolve this issue. One of the techniques I wanted to eliminate was to make sure that there were no firewall port blocking issues. I had to scan for ports that were closed across the network. Typically I run an IP packet scan using Microsoft network monitor or implement a firewall report. Then sift through countless lines of log information attempting to identify blocked ports that DFS requires. I came across an excellent Microsoft utility to scan for ports across the network. The utility reduces log analysis for you. The utility is called PortQryUI which is a port scanning program with a graphical user interface (GUI). This software helped me identify a couple of obscure ports that were closed and needed to be opened. I wish I would have had this program long ago. Oh and the price is FREE! You have to love that! Anyway, I know that this utility will one day help you in your network troubleshooting efforts. Here is how it works:

   1. First download PortQryUI from Microsoft to your Desktop by clicking here.

   2. Now double click on PortQryUI.exe to install the program.

   3. Now navigate to where the files were extracted to and double click on portqueryui.exe to start the program.

   4. First thing you need to do is type in the IP address of the target computer or device you want to communicate with.

Scan for Ports - Step 1

Scan for Ports - Step 1

   5. Next you need to select the type of network service you want to scan. You have two options. You can select from a predefined list of Ports as indicated in the drop down list or you can manually enter the ports to scan in the second option.

Scan for Ports - Step 2

Scan for Ports - Step 2

   6. Next Click on the Query button to begin scan for ports process.

   7. Once the results have been generated you need to save the results to Notepad. To do so click on File then Save Result selection. Save the file with a .log extension to indicate a log file.

Scan for Ports - Step 3

Scan for Ports - Step 3

   8. Now open your new log file for review. As you can see in my example below ports 135 and 636 are closed. Armed with this information I know that I can make firewall adjustments to allow those two ports through which intern allows the Domains and Trusts to communicate back and forth.

Scan for Ports - Step 4

Scan for Ports Results

That concludes How-to Scan for Ports across the network to identify if certain ports are closed for the applications you use. I also wanted to note that in the documentation it says that the supported operating systems are Windows 2000, Windows Server 2003 and Windows XP. I did install it in Windows 2008 R2 64Bit environment and it worked perfectly fine for me. I hope this utility helps you in the future. If you have any questions or would like to add to the post please leave a comment below. Thank you for taking the time to read this article.