How to get TCP server client mac address on ESP8266

Running a TCP server on ESP-07S for linking network to serial.
I need to read the mac address of the connecting client to save as an ID.
I cannot use the IP address, which is readily available in the tcpclient object, since it will not be unique. Probably the same address for most clients connecting to the ESP (given out by DHCP).

Is there some way to get at the MAC address of a TCPClient connection?
I am using ESP8266WiFi 2.4.1 library

OK, so it is possible to get at the MAC address via

stat_info = wifi_softap_get_station_info();

provided we run in AP mode, right?
If in STA mode, not possible?
(both the WiFi board and the client are connected to an existing WiFi router).