Mac Terminal NetStat
netstat(1) only tells you about the connections local to the machine you are running it on. So if you can run netstat on the gaming server, then you can find out the IP's of the clients. Look for connections to the game servers port. 

If you are looking to find out the ping time or lag for each of the clients I'm not sure there is a good way unless you are running on the game server, and then you may get an idea of the lag by getting the IP addresses of the clients and then running ping(8) on each of the addresses.