Long polling

Reading inquiries

In long polling, the CometVisu connects to the backend and leaves it open until the backend sends data. The initial request for all values is answered immediately by the backend. Subsequent requests will be answered as soon as a new value arrives. This is then sent to the CometVisu, whereupon the connection is closed and immediately rebuilt.


A special feature here is the internal Watchdog to call, which automatically ends a long polling request and restarted if no answer has come within 60 seconds.

Writing inquiries

If 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.