How can i chat with a person whose IP address is only known to me?

actually i am using meu torrent and when i download from the peer or peer download form me it shows there ip address. but i want to chat with those IP addresses and wanna find out which r the other torrent they r downloading etc etc......

I'm not familiar with that program, but generally speaking if that functionality is not built into your program, it will be difficult (and possibly illegal) to accomplish this. You can easily port scan the IP to see if they have the ports used for instant messenger programs open, but I don't know anything short of packet sniffing that will give you the screen name currently logged in from a particular IP address.

There is a small chance that they have the same client, and an even smaller chance that your client or their client supports chat between ip address.

I do not know, your best guess is to get a messenger such as yahoo, msn, aim
I just have this sneaky feeling that your hacking....I tried to do the same on my girlfriends computer WITH HER KNOWLEDGE but it didn't work