I'm not a windows expert, but there is Netstat. Sleepless suggested Wireshark, but as I commented earlier, this program has a definite learning curve to it.
LW 5 hides uses psuedo names instead of listing the address. The numbers are usually the last digits in their real address. Unless I'm mistaken, LW 5.3.6 does give option to find their ip address but cannot remember if that only applies to downloads or also uploads. ie: right-click the file & choose View Info & then the Transfer tab.

I think FrostWire & WinMX both allowed you to see their ip address. Might need to enable that in the upload window table view column options.