This usually means that the client helper program, hserver, is not running.

On Windows, verify that you have the service HoudiniServer listed in Services and that it has started. You can go to Services through Control Panel->Administrative Tools. If it's not listed, ensure that there is a program called hserver.exe located in C:\Windows\system32.

On Linux, make sure that hserver is listed in the process list. If not, you can start it by typing hserver when you've sourced the Houdini environment.

Houdini is using a Houdini License Server (sesinetd.exe) and a Houdini License Client (hserver.exe) to verify its licensing. Houdini uses TCP/IP to communicate with these processes, and if it unable to connect to either of them, it prints error messages. There are a few reasons why Houdini is not able to connect to hserver. The most common reasons are:

• Houdini License Server (sesinetd/sesinetd.exe) is not running
• Houdini License Client (hserver/hserver.exe) is not running
• The firewall blocks the communication on ports 1714 and 1715
• If installing the license server and client on the same machine, it could be that Houdini wasn't installed using administrative privileges(root/Administrator).