Is it possible to print client IP or MAC address from Arduino WiFi web server?
***** Assuming it is an ESP8266 based WI-FI shield: *****

Wifi shield > PC

Open serial monitor. Baud rate 155200. Also check COM ports.

Test AT commands by typing AT.

If it responds OK, you're good.

Type AT+CIFSR for IP adress.

Full list of AT commands in this link:

http://www.pridopia.co.uk/pi-doc/ESP8266ATCommandsSet.pdf