LGTV_BootloaderAccess.cs

using System;
using System.IO.Ports;
using System.Threading;

namespace LGTV_BootloaderAccess
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            var port = new SerialPort("COM2", 115200, Parity.None, 8, StopBits.One);

            var responded = false;

            port.DataReceived += (sender, e) =>
            {
                var output = port.ReadExisting();

                if (output.Contains("#"))
                {
                    responded = true;
                }

                Console.Write(output);
            };

            port.Open();

            var rnd = new Random();

            while (true)
            {
                if (responded)
                {
                    break;
                }

                var buffer = new byte[32];

                rnd.NextBytes(buffer);

                port.Write(buffer, 0, buffer.Length);
                Thread.Sleep(5);
            }

            Console.BackgroundColor = ConsoleColor.Red;
            Console.ForegroundColor = ConsoleColor.Yellow;
            Console.WriteLine("OK");

            Console.ReadKey(); // Any key to exit
        }
    }
}