Demo server is a fully-featured instance of Traccar which you can use to track your GPS devices or phones. Correct ports for your device can be found here. There are no limits on available features or number of devices. Demo servers don't have reverse geocoding and email service pre-configured. If you need those, check one of the paid options.
There is no pre-defined demo user or sample data. You need to register your own account by clicking on "Register" button on the login screen. To get some data you can use Traccar Client app on your smartphone.
At the moment there are several servers available. Feel free to choose any of them, but demo 1 is usually very busy as Traccar Client is configured to use it by default. Quality of service is not guaranteed, but we are trying our best to keep your GPS data safe and available to you at any time. At least a month of history should be available. If you want guaranteed uptime and full history for your servers, please check one of the paid options.