SendAsync不会每次都回复所有请求

Question

从下面的代码中，有时候，它不会回复所有的ping请求，并且会等待无限的时间。是否有任何死锁问题？如果是的话如何处理？如何在没有任何死锁的情况下为每个ip获得正确的结果？

class Program
    {        
        static Semaphore PingSender { get; set; }
        static object lockObj = new object();
        static void Main(string[] args)
        {
            long pingSent = 0;
            long pingReceived = 0;
            PingSender = new Semaphore(10000, 10000);

            for (int dotNoDot = 1; dotNoDot <= 255; dotNoDot++)
            {
                for (int dotNo = 1; dotNo <= 255; dotNo++)
                {
                    try
                    {
                        string ipAddress = string.Format("111.222.{0}.{1}", dotNoDot, dotNo);       //Please change necessary ip base
                        PingSender.WaitOne();
                        Ping ping = new Ping();
                        ping.PingCompleted += (sender, eventArgs) =>
                        {
                            //lock (lockObj)
                            //{
                                PingSender.Release(1);
                                Console.WriteLine(string.Format("{0}) Address: {1} and Status: {2}", pingReceived, eventArgs.UserState, eventArgs.Reply.Status));
                                if (eventArgs.Reply.Status == IPStatus.Success)
                                {
                                    //collect online machines
                                }
                                Interlocked.Increment(ref pingReceived);
                                if (pingReceived == pingSent)
                                {
                                    //done
                                }
                            //}
                        };
                        //lock (lockObj)
                        //{
                            pingSent++;
                       // }
                        ping.SendAsync(ipAddress, 10000, ipAddress);                       

                    }
                    catch (Exception ex)
                    {

                    }

                }
            }           
        }
}