My system consists of several ESP8266 based 'stations', which are synchronised in a way that all of them go into deep sleep and wake up on the same schedule. All stations are WiFi clients. All stations run on batteries and energy saving is critical.
One of the stations is a Master. It contains a modem/router that serves as AP to all stations. The AP is switched OFF during the sleep phase. When a Master wakes up it switches on the AP and thus starts a communication session available to all stations. When all stations have their data sessions completed and disconnect from AP, the Master switches off the modem/router and goes to sleep.
My question is about the Master being informed that there are no other clients actively connected to the AP. My current solution is WAN based - each station reports to the Web Service on the start and end of their connection. Is it possible to achieve the same result locally - by a request from the WiFi client to the Access Point?