PingException occurred mscorlib.dll

private static async Task AsyncPingTask(List<string> ipaddress)
        {
            try
            {
                Console.WriteLine("Ping Started");
                StringBuilder pingStringBuilder = new StringBuilder();


                    var pingTasks = ipaddress.Select(ip =>
                    {
                        using (var ping = new Ping())
                        {
                            return ping.SendPingAsync(ip);
                        }
                    }).ToList();

                    Console.WriteLine("Ping Completed");

                    await Task.WhenAll(pingTasks);


                    foreach (var pingReply in pingTasks)
                    {
                        pingStringBuilder.Append(pingReply.Result.Address);
                        pingStringBuilder.Append("-->");
                        pingStringBuilder.Append(pingReply.Result.Status);
                        pingStringBuilder.Append("-->");
                        pingStringBuilder.Append(pingReply.Result.RoundtripTime.ToString());
                        pingStringBuilder.AppendLine();
                    }
                    Console.WriteLine(pingStringBuilder.ToString());
                    pingStringBuilder.Clear();                

            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message.ToString());
                throw;
            }

            }

public static void Main()
        {
            List<string> address = new List<string>();
            Task t = Task.Run(() =>
            {
                var reader = new StreamReader(File.OpenRead(Environment.CurrentDirectory+@"\address.csv"));
                while (!reader.EndOfStream)
                {
                    var lines = reader.ReadLine();
                    var values = lines.Split(';');
                    address.Add(values[0]);
                }                
            });


            Console.WriteLine("List COunt is {0}",address.Count);
            Stopwatch timeSpan=Stopwatch.StartNew();


            t.Wait();            


            AsyncPingTask(address).Wait();

            Console.WriteLine(timeSpan.ElapsedMilliseconds);                        
            Console.ReadLine();
        }