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License Server - Client/Server connectivity   

Verify Connectivity

Issues with client-server licensing can often be traced to communication issues that prevent the client PC and server from communicating. The first step is to verify whether the client PC can connect to the license server over the licensing ports.

Even if you successfully establish connectivity, remember that server configuration or license issues can also keep a client PC from becoming licensed. See our Troubleshooting Tips article for guidance.

Basic connectivity (ping test)

On the client PC, click the Start button or press the Windows key, then type “cmd” into the search box in the Start menu, and press Enter. Windows will search for and open the Command Prompt.

From the command prompt, enter ping [server name or IP address]. For example, if your license server has a local IP address of, then type on the command line ping

If you are referencing your license server by name in FlexSim software’s License Activation interface, use the same fully qualified domain name here instead of the IP address:


If your client PC receives a response from your license server, then the server is visible across the network, by name or IP address, from the client PC.

Advanced connectivity (port test via telnet)

If you can pass the ping test you can then use telnet to determine if the client PC can communicate with the license server over the ports specified in the .lic file.

We have a tutorial video at that takes you through the basic steps of enabling telnet on your client PC, then using it to test port connections to your license server.

Double check your configurations

If you can't establish a ping connection or a port connection, use the suggestions below to double-check your settings. Or perhaps you passed the connection verification checks but FlexSim Software is still not getting licensed? These connectivity tips may reveal the solution:

CLIENT PC SETTINGS - You may have a typo or otherwise have misconfigured the settings that point your client PC to the license server. Double check that your settings are entered using the correct format (single-user client PC, multi-user client PC).

PORT & ADDRESS - Double check the port number and server address/name used in activating licenses on your client PC. Make the port number specified is the number in use for your license service. Our default port number is 26914 but enter your custom port number if you set your own.

SERVER FIREWALL - Did you add the required exceptions to your license server’s firewall (lmtools, lmadmin)? To any other network appliances and firewalls (lmtools, lmadmin)?

Connectivity suggestions

You've triple-checked your client PC settings. You've set firewall exceptions. The port test still shows that you can't connect from the client PC to the server. What can you do?

These aren't fixes, but they can help you narrow the source of the problem so that you can find a solution.

CHECK THE LICENSE SERVER - Maybe your license server isn't actually serving your licenses. You can install the FlexSim simulation software locally on your license server, then using the port you specified (default is 26914) and the local IP address, you can point your local FlexSim installation to the local license server to see if your license server can license itself. If it can't, check out these license-server troubleshooting tips (where you'll also read about this local test troubleshooting method).

DISABLE FIREWALLS (temporarily as a test) - A connection issue could be caused by a firewall configuration problem on the client PC, on the license server, or on some network appliance in between. One at a time, disable intervening firewalls on the client PC, the license server, and appliances in-between, as applicable. With each disabled firewall, retest connectivity. If connectivity is established after disabling a firewall, work on that firewall's configuration, then reenable it. Test again. Repeat for each firewall until a connection between client and server can be established.

DISABLE ANTI-VIRUS (temporarily as a test) - Some anti-virus solutions will block application communications. Disable anti-virus software on the client PC. If nothing changes, also disable anti-virus on the server. If this fixes the issue, work with your IT administrator to modify your anti-virus settings. Remember to reactivate your anti-virus software after this experiment.

ASK YOUR FRIENDLY NEIGHBORHOOD ADMIN - Your network may have settings, topology, filtering, etc. that affect the client PC’s ability to communicate with the license server. Work with your network administrator to make sure the client PC can communicate with the license server across your network using both port numbers - for the licensing service and the vendor daemon. See default and custom port numbers.

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