@bekesizl: It’s still freezing at night times in Germany and I’m not running OpenSprinkler right now to water the garden. It might be interesting, if the issue still exists with a wired Ethernet connection. Unfortunately, my OpenSprinkler V3.0 hardware model doesn‘t allow to attach an Ethernet module.
I‘ve also a backup system consisting of an ESP32 module, using Weather Underground weather reports to calculate the water level according to the Zimmerman method. The calculating result is send to the OpenSprinkler, running in manual mode. So, it’s a good idea to use such a workaround.
What I can think about is, that the “Empty Response”- issue is caused by some timing problem within the Arduino WiFi library function. I don’t know if this is the case and how to continue with the investigation?
However, for the time being my Local Weather Service runs with three or four data losses per day and can be well used to control the OpenSprinkler garden watering.