ULX only logs IPs on player connection if you have logging enabled in the ULX server.ini (it is by default)
See your data/ulx_logs folder
If you're looking for some type of logger for any type of connection to your machine, you'll have to find some other program.
I just recently installed PeerGuardian 2 on another machine I use, and was reminded that it could not only track denied IPs, but all connection attempts successful or not, inbound or out. Theoretically, you could configure it to not block any IPs and save those logs.