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

class Server
{
    static void Main()
    {
        TcpListener server = new TcpListener(IPAddress.Any, 8888);

        try
        {
            server.Start();
            Console.WriteLine("Сервер запущен");

            while (true)
            {
                TcpClient client = server.AcceptTcpClient();
                NetworkStream stream = client.GetStream();

                byte[] buffer = new byte[1024];
                int bytes = stream.Read(buffer, 0, buffer.Length);

                string text = Encoding.UTF8.GetString(buffer, 0, bytes);
                Console.WriteLine($"Получено: {text}");

                string response = $"OK: {StrProc(text)}";
                byte[] data = Encoding.UTF8.GetBytes(response);
                stream.Write(data, 0, data.Length);

                stream.Close();
                client.Close();
            }
        }
        catch (Exception e)
        {
            Console.WriteLine($"Ошибка: {e.Message}");
        }
        finally
        {
            server.Stop();
        }
    }

    //18 вариант
    private static string StrProc(string str)
    {
        return str.Replace('y', 'o');
    }
}