Program.cs

using System;

class Program
{
    static void Main(string[] args)
    {
        int port = 5000;
        Console.WriteLine("Port: " + port);
        Console.Write("Run as (S)erver or (C)lient? ");
        string mode = Console.ReadLine().ToUpper();

        if (mode == "S")
        {
            Server server = new Server("0.0.0.0", port);
            server.Start();
        }
        else if (mode == "C")
        {
            Console.Write("Enter server IP: ");
            string ip = Console.ReadLine();

            Console.Write("Enter username: ");
            string username = Console.ReadLine();

            while (string.IsNullOrWhiteSpace(username) || username.Contains(" "))
            {
                Console.Write("Invalid username, try again: ");
                username = Console.ReadLine();
            }

            Console.Write("Enter Password: ");
            string password = Console.ReadLine();

            Client client = new Client();
            client.Connect(ip, port, username, password);
        }
    }
}