I'm working on an app that uses HomeKit-enabled accessories such as wall plugs to control a photographic enlarger in a darkroom. This requires precise timing when toggling the power state of the plug. For example, the timer in my app might be set to 5 seconds, so I turn on the plug using writeValue() on the plugs power state characteristic, wait 5 seconds, then turn it off again.
I want to be able to measure if the plug actually responded to the command and if there was any delay in the plug actually turning on/off so I can display a warning to the user if network latency resulted in the plug being on for longer than the set time.
Does writeValue() (in my case, the async/await version) only return when the plug has been turned on, or does it return as soon as the command has been sent, regardless of if it has been received/acted on? Is there a way I can (a) quickly verify that the plug has been turned on/off, and (b) measure how long it took for the plug to act on the request, that is, the time elapsed between when writeValue() is called and when the plug actually updates to the corresponding value?