P2P Theory vs Practical

[theChameleon]

im a computer science grad, and have studied a module that briefly touched on P2P. let me say again, briefly.

so, it's all about DHT, Chord, yada yada yada. all theoretical.

i have one question...

how do u find the FIRST node in the P2P network in the practical sense? how do u get the FIRST IP with the file u want without a tracker?

thanks.