If you don't need the possibility to connect to your NoMachine server via the web (this feature is not available with NoMachine free version), you may stop the web server (nxhtd) and disable the automatic startup at reboot. Administrative privileges are requested to complete such operations.
To do that:
1. Open the NoMachine server preferences UI:
click on the !M icon in the system tray to open the menu. Then click on Show the service status and finally on Server preferences or
launch NoMachine from your program menu, click on Settings and then on the Server preferences link at the bottom of the panel.
2. In the 'Services' panel of the UI, select service 'HTTP' and click on the 'Configure' button.
3. In the configuration panel set: Start mode manual and click on the 'Stop' button to stop the web server.
Both the HTTP and the HTTPS service will be stopped and will be not restarted at the next reboot.
You can re-enable the service at any moment via the UI.
If you prefer to perform these operations from command line, you can use the nxserver commands.
For example on Linux and Mac execute:
sudo /etc/NX/nxserver --stop nxhtd && sudo /etc/NX/nxserver --startmode nxhtd manual
if you want to restart the web server and ensure that it's started automatically at every reboot, execute:
sudo /etc/NX/nxserver --start nxhtd && sudo /etc/NX/nxserver --startmode nxhtd automatic