How to dispose threads in window application

public void startClient(TcpClient inClientSocket, string clineNo)
{
   //string strclientIp = inClientSocket.Client.RemoteEndPoint.ToString();
   this.clientSocket = inClientSocket;
   this.clNo = clineNo;

   //t.Join(2000);
   Thread ctThread = new Thread(doChat);
   ctThread.Start();
}
private void doChat()
{
   while ((!shutdown ))
   {
      try
      {
         requestCount = requestCount + 1;
         NetworkStream networkStream = clientSocket.GetStream();
         networkStream.Read(bytesFrom, 0, (int)clientSocket.ReceiveBufferSize);
         Thread.Sleep(2000); 
         delSave(dataFromClient);
         clientSocket.Client.Close();
         networkStream.Flush();
      } catch{}
   }
}