UDP ESP8266-12 AP with multiple ESP8266-12 STA

Hi Everyone

I've been running 3 'clients' (STA) using UDP successfully, connected to my Arduino Mega2560 Access Point (AP) but have noticed that the IP addresses allocated to each client do not remain the same at every boot of the sytem. The first client to connect is allocated the first IP address of 192.168.4.2, the second client to connect is allocated IP address 192.168.4.3 & so on.
The problem is that on booting the system the first client to connect is not always client1

Is there a way to set a static UDP IP address for each of the clients so regardless of which client connects first the IP address remains associated with the same client ie client1 always has the same IP address of 192.168.4.2, client2 always has the same IP address of 192.168.4.3 etc?

ps I'm not interested in an internet (IoT) connection just sending data over my local WLAN

The access point IP address stays the same at 192.168.4.1