C# - IP return 함수

        //사설 ip
        public static string GetInternalIPAddress()
        {
            var host = Dns.GetHostEntry(Dns.GetHostName());

            foreach (var ip in host.AddressList)
            {
                if (ip.AddressFamily == AddressFamily.InterNetwork)
                {
                    return ip.ToString();
                }
            }

            throw new Exception("No network adapters with an IPv4 address in the system!");
        }
        
        //공인 ip
        #region GetRealIpAddress

        private string GetRealIpAddress()

        {
            IPAddress gateway = FindGetGatewayAddress();


            if (gateway == null)

                return null;



            IPAddress[] pIPAddress = Dns.GetHostAddresses(Dns.GetHostName());



            foreach (IPAddress address in pIPAddress)

                if (IsAddressOfGateway(address, gateway))

                    return address.ToString();



            return null;

        }



        private bool IsAddressOfGateway(IPAddress address, IPAddress gateway)

        {

            if (address != null && gateway != null)

                return IsAddressOfGateway(address.GetAddressBytes(), gateway.GetAddressBytes());



            return false;

        }



        private bool IsAddressOfGateway(byte[] address, byte[] gateway)

        {

            if (address != null && gateway != null)

            {

                int gwLen = gateway.Length;



                if (gwLen > 0)

                {

                    if (address.Length == gateway.Length)

                    {

                        --gwLen;

                        int counter = 0;



                        for (int i = 0; i < gwLen; i++)

                        {

                            if (address[i] == gateway[i])

                                ++counter;

                        }



                        return (counter == gwLen);

                    }

                }

            }



            return false;

        }



        private IPAddress FindGetGatewayAddress()

        {

            IPGlobalProperties ipGlobProps = IPGlobalProperties.GetIPGlobalProperties();


            foreach (NetworkInterface ni in NetworkInterface.GetAllNetworkInterfaces())

            {
                IPInterfaceProperties ipInfProps = ni.GetIPProperties();



                foreach (GatewayIPAddressInformation gi in ipInfProps.GatewayAddresses)

                    return gi.Address;

            }



            return null;

        }

        #endregion