This CSharp (C#) code snippet shows how to get the external IP address (IPv4) of a machine (i.e. dialup connection IP). To achieve this we get all ip addresses of the machine and compare them against the local address ranges (10.0.0.0/24, 172.16.0.0/16, 192.168.0.0/16 and 169.254.0.0/16).
private IPAddress GetExternalIPAddress()
{
IPHostEntry myIPHostEntry = Dns.GetHostEntry(Dns.GetHostName());
foreach (IPAddress myIPAddress in myIPHostEntry.AddressList)
{
byte[] ipBytes = myIPAddress.GetAddressBytes();
if( myIPAddress.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork )
{
if (!IsPrivateIP(myIPAddress))
{
return myIPAddress;
}
}
}
return null;
}
private bool IsPrivateIP(IPAddress myIPAddress)
{
if (myIPAddress.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork)
{
byte[] ipBytes = myIPAddress.GetAddressBytes();
// 10.0.0.0/24
if (ipBytes[0] == 10)
{
return true;
}
// 172.16.0.0/16
else if (ipBytes[0] == 172 && ipBytes[1] == 16)
{
return true;
}
// 192.168.0.0/16
else if (ipBytes[0] == 192 && ipBytes[1] == 168)
{
return true;
}
// 169.254.0.0/16
else if (ipBytes[0] == 169 && ipBytes[1] == 254)
{
return true;
}
}
return false;
}
private bool CompareIpAddress(IPAddress IPAddress1, IPAddress IPAddress2)
{
byte[] b1 = IPAddress1.GetAddressBytes();
byte[] b2 = IPAddress2.GetAddressBytes();
if (b1.Length == b2.Length)
{
for (int i = 0; i < b1.Length; ++i)
{
if (b1[i] != b2[i])
{
return false;
}
}
}
else
{
return false;
}
return true;
}