Server sent events (SSE)¶
At Server sent events, a one-time read connection is established. Initially, the backend sends all the requested values once, then only changed values.
The browser automatically takes care of the restoration of the connection in case of abortions. Therefore, the internal Watchdog is usually not used in SSE.
However, the browser must support this technology. An overview of the supported browsers is provided by Caniuse.
When a new value is to be sent to the backend (because, for example, the user has serviced a widget), a new request that is completely independent of the read requests is sent to the backend. Here, the backend only confirms the successful receipt of the request, new values are always sent only via the read requests.