Iper is a plugin that gives you player name and ip. When a player joins the server it saving his ip in a yml file which call ip.yml! Also it says to console for a example : [INFO] Player theodossis was added to the ip.yml
Example ip.yml:
theodossis: 192.168.1.38:60423:60423
Installation:
Download the latest iper.jar
Place it to your bukkit plugins' file
(Re)Start your server
Successfully installed!