The API provides a websocket at /msgs to update volatile data asynchronously. The data to be sent over the websocket is controlled with a subscription model. With the sat-nms Software, everything is about device parameters: Every device parameter has a unique ID, changes of this parameters are transported as messages having the id and the value of this parameter as properties. The websocket is used one-way: There are only messages sent from the backend server to the front end. The /api/v1/subscribe API call controls which messages / parameters shall be send over the websocket.