So private IP addresses are 192.168.00 ~ 192.168.255.255 or 10.0.0.0 or 172.16.0.0 ~ 172.31.255.255 If I accepted a client to my serversocket, I can get the client's remoteIp address by using socket.getremotesocketaddress(); But I suspect the IP address that I'm getting from this method is only the public IP address and it must have more than one client using same public IP as this one (one like you see when you go on to the website www.whatismyip.com). So if I want to make sure that my packet is delivered to the right person using some IP address or otherthing that uniquely identifies a person, what should I have to do?