How to get username of computer

I need to get username of any computer by using ipaddress
or system name


Get hostname from ipaddress
IPHostEntry ip2 = Dns.GetHostEntry("192.168.1.2");
string hostname = ip2.HostName;

Getipaddress from hostname
string ipaddress = Dns.GetHostAddresses("hostname")[0].ToString();

I need to get systemname by using ipadress or hostname