How can my WCF service get a client's IP address?

/* HTTP POST Payload Receiver WCF Web Service written by Erik Hensens
 * This executible server accepts the text payload of an HTTP POST
 * and saves it as a uniquely dated XML file */
 
/* To properly run this program in Windows Vista, all firewalls including
 * Windows Firewall needs to be configured to allow communication through
 * the desired port or completely disabled.
 *
 * In addition, the application must be opened by right-clicking and
 * selecting "Run as administrator" 
 * 
 * Please see Readme.txt */
 
 
 
using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Net;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.ServiceModel.Activation;
using System.ServiceModel.Channels;
using System.ServiceModel.Description;
using System.ServiceModel.Dispatcher;
using System.ServiceModel.Web;
using System.Text;
using System.Web;
using System.Xml;
 
public class getString
{
    [ServiceContract]  
    public interface IService
    {
        [OperationContract]
        [WebInvoke]
        void SaveString(Stream stream);  
    }  
 
        public class Service : IService  
        {  
            public void SaveString(Stream text)
            {
                /* stringText is POST payload stream converted to type string */
                StreamReader streamReader = new StreamReader(text);
                string stringText = streamReader.ReadToEnd().Replace('*', '\n'); ;
                streamReader.Dispose();
                
                string currentTime = DateTime.Now.ToString();
                logData("\n" + currentTime + ": Request received");
 
                string currentTimeFormatted = DateTime.Now.ToString().Replace('/', '-').Replace(' ', '_').Replace(':', '_');
                string currentFileName = "POSTPayload_" + currentTimeFormatted + ".xml";
                string currentDirectory = System.IO.Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().Location);
                string desiredXmlFolder = "XMLResults";
 
                string fileHeaderMessage = "<!-- File auto-generated at: " + currentTime + " -->";
 
                StreamWriter streamWriter = new StreamWriter(desiredXmlFolder + "\\" + currentFileName);
                streamWriter.WriteLine(fileHeaderMessage + "\n\n" + stringText);
                streamWriter.Close();
 
                int currentFileSize = stringText.Length + fileHeaderMessage.Length + 4;
                logData("HTTP POST payload saved as file:\nName: " + currentFileName + "\nDirectory: " + (currentDirectory + "\\" + desiredXmlFolder) + "\nExpected File Size: " + currentFileSize + " bytes");
 
                /* Get parameter values */
                int parameterID = getParameterID(stringText);
                int ParameterSpec;
                int ParameterHighRange;
                int ParameterLowRange;
 
                switch (parameterID)
                {
                    case 1:
                        ParameterSpec = 5;
                        ParameterHighRange = 50;
                        ParameterLowRange = 1;
                        break;
                    case 3:
                        ParameterSpec = 20;
                        ParameterHighRange = 30;
                        ParameterLowRange = 10;
                        break;
                    case 4:
                        ParameterSpec = 100;
                        ParameterHighRange = 50;
                        ParameterLowRange = 150;
                        break;
                    case 6:
                        ParameterSpec = 0;
                        ParameterHighRange = -50;
                        ParameterLowRange = 50;
                        break;
                    default:
                        ParameterSpec = -1;
                        ParameterHighRange = -1;
                        ParameterLowRange = -1;
                        break;
                }
 
                Console.WriteLine("\n\n{0}\n{1}\n{2}\n\n", ParameterSpec, ParameterHighRange, ParameterLowRange);
 
                Console.WriteLine("\n\n\nService running...\nPress <ENTER> To Exit\n\n");
            }  
        }
 
    static Binding GetBinding()  
    {
        BasicHttpBinding binding = new BasicHttpBinding()
        {
            TransferMode = TransferMode.StreamedRequest
        };
        binding.MaxReceivedMessageSize = 10000000;
        binding.MaxBufferSize = 10000000;
        return binding;
    }
 
    /* Write data on console and save it in log file */
    public static void logData(string incomingData)
    {
        StreamWriter logDataSW = File.AppendText("log.txt");
        logDataSW.WriteLine(incomingData);
        logDataSW.Close();
        Console.WriteLine(incomingData);
    }
 
    /* Get the POST payload's parameter ID */
    public static int getParameterID(string stringText)
    {
        /* Find the stringText indeces of <P> </P> */
        for (int payloadIndex = 0; payloadIndex < stringText.Length; payloadIndex++)
        {
            /* If <P> is found */
            if (stringText[payloadIndex] == '<' && stringText[payloadIndex + 1] == 'P' && stringText[payloadIndex + 2] == '>')
            {
                char paramIDchar = stringText[payloadIndex + 3];
 
                /* (int)paramIDchar will be the ASCII value, so subtract 48, the ASCII of '0' */
                return (int)paramIDchar - 48;
            }
 
            /* If <P> is not found (fatal error) */
            if (payloadIndex == stringText.Length)
            {
                Console.WriteLine("\n\nFatal error: Payload does not contain <P> indicator\n\n");
                Environment.Exit(1);
            }
        }
        return 0;
    }
 
    public static void Main()
    {
        //string baseAddress = "http://10.2.2.61:8004/Service";
        string baseAddress;
        string ipv4;
        string port;
        string directory;
 
        /* If either data.txt or log.txt does not exist, create it */
        if (!File.Exists("data.txt"))
        {
            StreamWriter tempDataSW = File.CreateText("data.txt");
            tempDataSW.Close();
        }
        if (!File.Exists("log.txt"))
        {
            StreamWriter tempLogSW = File.CreateText("log.txt");
            tempLogSW.Close();
        }
 
        /* Set Read-only to false for writeable text files */
        FileInfo dataInfo = new FileInfo("data.txt");
        FileInfo logInfo = new FileInfo("log.txt");
        dataInfo.IsReadOnly = false;
        logInfo.IsReadOnly = false;
 
        /* Load the default baseAddress to use */
        StreamReader defaultBaseSR = File.OpenText("data.txt");
        baseAddress = defaultBaseSR.ReadLine();
        defaultBaseSR.Close();
        
        Console.WriteLine("HTTP POST Payload Receiver\nWCF Web Service\n");
        
        /* If this is the very first run, get the default baseAddress to use */
        if (baseAddress == null)
        {
            Console.WriteLine("\nEnter IPv4 Address Information:\n");
            Console.WriteLine("\nUSEAGE:    http://<IPv4>:<Port>/<Directory>\n\nNOTE: User should enter \"Service\" for Directory\n");
            Console.Write("\nIPv4:      ");
            ipv4 = Console.ReadLine();
            Console.Write("Port:      ");
            port = Console.ReadLine();
            Console.Write("Directory: ");
            directory = Console.ReadLine();
            baseAddress = "http://" + ipv4 + ":" + port + "/" + directory;
            Console.Write("\n");
 
            StreamWriter firstTimeAddressSW = File.AppendText("data.txt");
            firstTimeAddressSW.WriteLine(baseAddress);
            firstTimeAddressSW.Close();
        }
 
        WebServiceHost host = new WebServiceHost(typeof(Service), new Uri(baseAddress));
        host.Open();
 
        Console.WriteLine("Default Web Host: {0}\n", baseAddress);
        Console.WriteLine("\nMenu\n\n1 - Modify Web Host\n2 - Exit\nPress <ENTER> To Run\n");
 
        string userChoice = Console.ReadLine();
        if (userChoice == "1")
        {
            Console.WriteLine("\nUSEAGE:    http://<IPv4>:<Port>/<Directory>\n\nNOTE: User should enter \"Service\" for Directory\n");
            Console.Write("\nIPv4:      ");
            ipv4 = Console.ReadLine();
            Console.Write("Port:      ");
            port = Console.ReadLine();
            Console.Write("Directory: ");
            directory = Console.ReadLine();
            baseAddress = "http://" + ipv4 + ":" + port + "/" + directory;
            Console.Write("\n");
            
            /* Re-write default baseAddress */
            StreamWriter rewriteAddressSW = new StreamWriter("data.txt");
            rewriteAddressSW.Write(baseAddress);
            rewriteAddressSW.Close();
            Console.WriteLine("Program will now need to restart...\n");
            Console.ReadLine();
            Environment.Exit(1);
 
        }
        else if (userChoice == "2")
            Environment.Exit(1);
        else { }
 
        Console.WriteLine("Web Host: {0}\n", baseAddress);
 
        WebClient client = new WebClient();
        client.Headers[HttpRequestHeader.ContentType] = "text/plain";
        Console.WriteLine("Service running...\nPress <ENTER> To Exit\n");
        Console.ReadLine();
        host.Close();
    }
}

                                  

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