Unable to Communicate With License Server Error in NI VLM

Updated Jul 19, 2019

Reported In


  • NI License Manager
  • Volume License Manager

Issue Details

I want to use an NI software product that is licensed through NI Volume License Manager (VLM). Whenever I launch the product, when attempting to connect to the license server I get the following message:

Unable to Communicate With License Server. 

My local licences in NI License Manager are in evaluation mode or appear as unlicensed. 


The client may not have network access

If the client does not have network access and cannot connect to a license server at all, you can generate a disconnected license file from NI VLM following the steps found in Create a Disconnected License for an Existing Computer in VLM.

Make sure the name you are entering matches the server name of the Volume License Server

You can verify this by talking to your software admin.  

The license server may be down

  • Ensure that the server computer is on and that the license server is running.
  • Verify that the license server is running without an error. This can be done by examining the log file or by stopping and restarting the server. 
  • If an error has occurred, you may get a message saying Unable to stop license server. In this case, stop the nilm.exe process through the Windows Task Manager. Then restart the license server.
  • Reboot the server.

The client computer may not be pointing to the correct license server port

  1. Check the port that the license server is running on (NI-VLM >> Tools >> Preferences >> System Settings).
  2. Ensure that the client computer is configured to look to that same port:
    1. Open NI License Manager by going to Start»All Programs»National Instruments»NI License Manager.
    2. Go to Top Left Tab>>Manage Volume License Server. 

    3. Ensure that the correct server name and port are configured (ports are specified using Server:##### syntax).
  3. If you cannot connect to the server you can do a Telnet connection test to test the connection between your client machine and the server by following Troubleshooting NI VLM Client Connection Issues Using Telnet.

The firewalls on the VLM server side may be blocking some or all of the ports necessary for client-server communication

The following instructions are for Windows 7, refer to Microsoft documentation for similar instructions in other operating systems: 
  1.  On the Start Menu in Windows, click Control Panel.
  2.  In Control Panel, click System and Security, and then open Windows Firewall.
  3. In Windows Firewall, click Advanced Settings, and then click Inbound Rules.
  4. On the right-hand side bar, select New Rule... to open the New Inbound Rules Wizard.
  5. Within the Wizard, configure the port rules such that TCP 27000 and 4637 are open, per the Configuring Software and Hardware Firewalls to Support National Instruments Products whitepaper. Note: these TCP ports correspond to the Main Licensing and Communication ports as configured in the NI Volume License Manager. Confirm the VLM ports that need to be opened in Tools >> Preferences >> System Settings.

NOTE: Firewall connections may be controlled by your IT Department or Computer Administrator. If the activation is not successful after configuring the ports, check with IT to see if they are blocked elsewhere.

The client may not be on the same domain as the license server

This error might occur if the client computer is connected to a license server which is on a different domain than the client computer. To resolve this, add the server's domain to the client computer's DNS settings. To do this, complete these steps on the client computer to verify the domain.

Additional Information

You can further troubleshoot VLM connectivity issues using the troubleshooting guide


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