You can get the client's IP address. The term URL doesn't make sense for a client. A URL is a resource locator, which what the client uses to find a webpage, service, etc.
I found the following solution
here[
^]:
string strHostName = System.Net.Dns.GetHostName();
IPAddress clientIPAddress = System.Net.Dns.GetHostAddresses(strHostName).GetValue(0);