Does hosting a game on "Lan wi-fi" require "uPnP"?

Suppose there are 3 Lan users A(192.168.0.2) , B(192.168.0.3) & C(192.168.0.4). All of them are coected with home wifi router R(192.168.0.1). Now suppose user A hosts counter-strike with IP as mentioned above and port "27015". How B&C will be able to coect to A because each time they send request to A that request will be dropped by router because A didn't send any data to them first. So for this A has to instruct router via "uPnP" that pass those packets which are coming for port "27015". If I'm not correct then tell me how Lan wi-fi users coect with each other for multiplayer?If "uPnP" is not valid here then how user B&C are able to coect with A? I guess using ARP?