PS1 | Serwer Echo

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

namespace Serwer_ECHO
{
    class Program
    {
        static void Main(string[] args)
        {
            bool tryAgain = true;
            byte[] data = new byte[1024];
            string input, stringData;
            Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

            while (tryAgain)
            {
                Console.Write("Which port you want to create server [7]? : ");
                string port = Console.ReadLine(); if (port == "") port = "7";

                try
                {
                    IPAddress ipAd = IPAddress.Parse("127.0.0.1");
                    TcpListener listen = new TcpListener(ipAd, int.Parse(port));

                    listen.Start();
                    Console.WriteLine("The local Endpoint is : " + listen.LocalEndpoint);
                    Console.WriteLine("Waiting for connection...");
                    tryAgain = false;
                    socket = listen.AcceptSocket();
                    String message;
                    Console.WriteLine("Connection accepted from " + socket.RemoteEndPoint);
                    while (true)
                    {
                        int k = socket.Receive(data);

                        if (k == 0) break;  // jeżeli wysłano pusty pakiet
                        else
                        {
                            message = Encoding.ASCII.GetString(data, 0, k);
                            if (message.Equals("App:CloseConnection", StringComparison.InvariantCultureIgnoreCase)) break;  // jeżeli wysłano komende zamkniecia polaczenia
                            Console.WriteLine(message);

                            StringBuilder res = new StringBuilder();
                            res.Append(message);

                            byte[] buffer = Encoding.ASCII.GetBytes(res.ToString());
                            socket.Send(buffer);
                        }

                    }
                    Console.WriteLine("\nClient has disconnected from server");
                    socket.Close();
                    listen.Stop();
                    Console.ReadLine();
                }
                catch (FormatException e)
                {
                    Console.Write("Unable to create server or port is not number, want to try with another port? [y/n]: ");
                    string ca = Console.ReadLine();
                    if (ca.ToLower() == "y" || ca.ToLower() == "yes") tryAgain = true;
                    else tryAgain = false;
                }
                catch (SocketException e)
                {
                    Console.WriteLine("Client has closed connection unproperly");
                    Console.WriteLine("or server has another instance running on this port.");
                    Console.ReadLine();
                }

            } //while (tryAgain)
        }   // main
    }   // class
}   // namespace