ASK about my project using ethernet arduino identify IP address

Hello,

i have a project, first the device will broadcast data to IP destination(arduino IP). After that i want my arduino identify the IP off the device that send the data.

what i must to use? can i use example from arduino? can some one tell me the step what i must to do first?(not the step make the program)

thanks before

After that i want my arduino identify the IP off the device that send the data.

The below discussion has some info.

http://forum.arduino.cc/index.php/topic,82416.0.html