Server not found

NEST Desktop cannot find the NEST Simulator. It has two possible reasons:

  • NEST Desktop has a wrong URL under which it tries to contact the server. (See the FAQ for NEST Simulator.)
  • NEST Server is not running. Try to (re-)start NEST Server.
  • Use simulation service (e.g. on EBRAINS): The user authorization to the backend might be not granted.


Check NEST Server is running (if the URL is localhost:52425):

  • in URL of Browser: http://localhost:52425
  • in Terminal: curl http://localhost:52425
  • in Python: import requests; requests.get('http://localhost:52425')

Internal server error

It says that the back end (i.e, nest-server) ended with an internal error. In this case, you have to review the log of the back end.

NEST error

NEST Simulator produces a value error, e.g. The value must be strictly negative.. Please have a look at the official NEST documentation to obtain the correct syntax for the commands.

Gateway Time-out

This means that the NEST Server did not receive a response from the NEST Simulator within a certain period of time.

If you are using NEST Desktop on EBRAINS: Our setup on EBRAINS is not ready for bigger simulations and may lead to this error if it takes too long.

Please reduce the load, e.g. by reducing the population size or the simulating time. It also helps to use a bigger simulation resolution.


Firefox private mode problems

When NEST Desktop is opened in a private window in Firefox, only a blank screen is shown. This is due to an internal configuration in Firefox. If you are an experienced user, you might have a look at the official issue for more information - but please keep in mind that the preliminary workaround mentioned there might result in your Firefox leaking data in private mode! For all other users, please use the normal mode in Firefox (and just cleanup the cookies afterwards) or use another browser, if you really need to use the private mode.