Hot to get IP Address from Remote system(visitors)

Hi

 This is Urgent Requirment for me,
 
  How to Access IP Address of Remote systems(visitors who access the site those IP ADDRESS)
     
  I searched my google every body saying about "REMOTE_ADDR" if i run from site its showing proxy server or server IP Address. that is not equal to my system IP Address.
 
  Please tell me if any possiblities

thx advance