using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Net.NetworkInformation;
using System.Threading.Tasks;

namespace SweePing
{
    class Program
    {
        static void Main(String[] args)
        {
            var p = new Program();

            var _stopWatch = Stopwatch.StartNew();
            p.PingSweepAsync("10.250.0.", 1, 254).GetAwaiter().GetResult();
            _stopWatch.Stop();
            Console.WriteLine($"{p.HostsUp} devices found! Elapsed time: {_stopWatch.ElapsedMilliseconds}ms");
            if (Debugger.IsAttached)
            {
                Console.WriteLine("Press ENTER to EXIT . . .");
                Console.ReadLine();
            }
        }

        private Int32 _timeout = 100;
        static Object LockObj = new Object();


        public Int32 HostsUp { get; set; } = 0;

        public async Task PingSweepAsync(String baseIp, Int16 start, Int16 end)
        {
            HostsUp = 0;

            var tasks = new List<Task>();

            for (var i = start; i <= end; i++)
            {
                tasks.Add(PingAndUpdateAsync(baseIp + i.ToString()));
            }

            await Task.WhenAll(tasks);
        }

        private async Task PingAndUpdateAsync(String ip)
        {
            var ping = new Ping();
            var reply = await ping.SendPingAsync(ip, _timeout);
            if (reply.Status == IPStatus.Success)
            {
                lock (LockObj)
                {
                    HostsUp++;
                }
            }
        }
    }
}