C#

// ServerApp.cpp : main project file.


using System;
using System.Net;
using System.Net.Sockets;
using System.IO;
using System.Threading;
using System.Collections;
using System.Text;
public static class GlobalMembers
{

    public const int ECHO_PORT = 8080;

    internal static void Main()
    {
        try
        {
            // Bind the server to the local port
            TcpListener clientListener = new TcpListener(ECHO_PORT);

            // Start to listen
            clientListener.Start();

            Console.WriteLine("Waiting for connections...");

            while (true)
            {
                // Accept the connection
                TcpClient client = clientListener.AcceptTcpClient();

                ClientHandler cHandler = new ClientHandler();

                cHandler.clientSocket = client;

                // Create a new thread for the client
                Thread clientThread = new Thread(new ThreadStart(cHandler.RunClient));
                clientThread.Start();
            }

            clientListener.Stop();
        }
        catch (Exception e)
        {
            Console.WriteLine("Exception: " + e);
        }
    }
}

public class ClientHandler
{
    public TcpClient clientSocket;
    public static Hashtable users = new Hashtable(30);

    public void RunClient()
    {
        // Create the stream classes
        StreamReader readerStream = new StreamReader(clientSocket.GetStream());
        NetworkStream writerStream = clientSocket.GetStream();

        string returnData = readerStream.ReadLine();
        string userName = returnData;

        // Add a user
        users.Add(userName, clientSocket);

        Console.WriteLine("Welcome " + userName + " to the Server");

        while (true)
        {
            returnData = readerStream.ReadLine();
            string tempData = returnData.ToLower();

            if (tempData.IndexOf("quit") > -1)
            {
                Console.WriteLine("Bye Bye " + userName);
                break;
            }

            Console.WriteLine(userName + ": " + returnData);
            returnData += "\r\n";

            Byte[] dataWrite = Encoding.ASCII.GetBytes(returnData);

            TcpClient[] tcpClients = new TcpClient[users.Count];
            users.Values.CopyTo(tcpClients, 0);
            for (int i = 0; i < tcpClients.Length; i++)
            {
                NetworkStream tempWriteStream = tcpClients[i].GetStream();
                tempWriteStream.Write(dataWrite, 0, dataWrite.Length);
            }
        }

        clientSocket.Close();
    }

}

using System; 
using System.Net; 
using System.IO; 
using System.Net.Sockets; 
using System.Text; 

public class EchoClient 
{ 
   const int ECHO_PORT = 8080; 

   public static void Main(string [] arg) 
   { 
      Console.Write("Your UserName:"); 
      string userName = Console.ReadLine(); 
      Console.WriteLine("-----Logged In----->"); 

      try 
      { 

         // Create a connection with the ChatServer 
         TcpClient eClient = new TcpClient("127.0.0.1", ECHO_PORT); 

         // Create the stream classes 
         StreamReader readerStream = new StreamReader(eClient.GetStream()); 
         NetworkStream writerStream = eClient.GetStream(); 

         string dataToSend; 

         dataToSend = userName; 
         dataToSend += "\r\n"; 

         // Send username to the server 
         byte[] data = Encoding.ASCII.GetBytes(dataToSend); 

         writerStream.Write(data,0,data.Length); 

         while(true) 
         { 
            Console.Write(userName + ":"); 

            // Read line from server 
            dataToSend = Console.ReadLine(); 
            dataToSend += "\r\n"; 

            data = Encoding.ASCII.GetBytes(dataToSend); 
            writerStream.Write(data, 0, data.Length); 

            // If QUIT is sent, then quit application 
            if (dataToSend.IndexOf("QUIT") > -1) 
               break; 

            string returnData; 

            // Receive response from server 
            returnData = readerStream.ReadLine(); 

            Console.WriteLine("Server: " + returnData); 
         } 

         // Close TcpClient 
         eClient.Close(); 
      } 
      catch(Exception exp) 
      { 
         Console.WriteLine("Exception: " + exp); 
      } 
   } 
}