c# -异步服务器vs同步服务器-套接字

我有一些奇怪的问题，两个c#服务器套接字。

我有2台服务器。一个是异步的，另一个是同步的。我也有客户端在android发送图片到这个服务器。

同步服务器:

Socket listener = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
public void Start()
{
    byte[] bytes = new Byte[1024000];
    String content = String.Empty;
    IPAddress ipAddress = IPAddress.Parse("192.168.1.2");
    IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 53100);
    try
    {
        listener.Bind(localEndPoint);
        listener.Listen(10);
        while (true)
        {
            //// Program is suspended while waiting for an incoming connection.
            Socket handler = listener.Accept();
            data = null;
            // An incoming connection needs to be processed.
            while (true)
            {
                bytes = new byte[1024000];
                int bytesRec = handler.Receive(bytes);
                strBuilder.Append(Encoding.ASCII.GetString(bytes, 0, bytesRec));
                if (strBuilder.Length > 1)
                {
                    content = strBuilder.ToString();
                    byte[] xdata = Convert.FromBase64String(content);
                    using (var mStream = new MemoryStream(xdata, 0, xdata.Length))
                    {
                        pictureBox1.Image = Image.FromStream(mStream, true);
                    }
                }
            }
            byte[] msg = Encoding.ASCII.GetBytes(data);
            handler.Send(msg);
            handler.Shutdown(SocketShutdown.Both);
            handler.Close();
        }
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message);
    }
}
private void Form1_Load(object sender, EventArgs e)
{
    thr = new Thread(new ThreadStart(Start));
    thr.Start();
}

异步服务器:

public void StartListening()
        {
            listener.Bind(new IPEndPoint(IPAddress.Parse("192.168.1.2"), 53100));
            listener.Listen(1);
            allDone.Reset();
            listener.BeginAccept(new AsyncCallback(AcceptCallback), listener);
        }
        public void AcceptCallback(IAsyncResult ar)
        {
            Socket listener = (Socket)ar.AsyncState;
            Socket handler = listener.EndAccept(ar);
            StateObject stateObj = new StateObject();
            stateObj.clientSocket = handler;
            handler.BeginReceive(stateObj.buffer, 0, StateObject.buffSize, 0, 
                new AsyncCallback(ReadCallback), stateObj);
            listener.BeginAccept(new AsyncCallback(AcceptCallback), listener);
        }
        public void ReadCallback(IAsyncResult ar)
        {
            String content = String.Empty;
            StateObject stateObj = (StateObject)ar.AsyncState;
            Socket handler = stateObj.clientSocket;
            SocketError errorCode;
            int bytesRead = handler.EndReceive(ar, out errorCode);
            if (errorCode != SocketError.Success)
            {
                bytesRead = 0;
            }
            if (bytesRead > 0)
            {
                stateObj.strBuilder.Append(Encoding.ASCII.GetString(stateObj.buffer, 0, bytesRead));
                handler.BeginReceive(stateObj.buffer, 0, stateObj.buffer.Length, SocketFlags.None, new AsyncCallback(ReadCallback), stateObj);
            }
            else
            {
                if (stateObj.strBuilder.Length > 1)
                {
                    content = stateObj.strBuilder.ToString();
                    Debug.WriteLine(content);
                    byte[] data = Convert.FromBase64String(content);
                    using (var mStream = new MemoryStream(data, 0, data.Length))
                    {
                        pictureBox1.Image = Image.FromStream(mStream, true);
                    }
                    recImage = (Bitmap)pictureBox1.Image;
                    imgImage = new Image<Bgr, Byte>(recImage);
                    imageBox1.Image = imgImage;
                    while (imageBox1.Image != null)
                    {
                        SURFDetectionAndGUIUpdate(this, new EventArgs());
                    }
                    string xname = name.ToString();
                    Send(handler, xname);
                }
            }
        }
        private void Send(Socket handler, String data)
        {
            byte[] byteData = Encoding.ASCII.GetBytes(data);
            handler.BeginSend(byteData, 0, byteData.Length, 0,
                new AsyncCallback(SendCallback), handler);
        }
        private void SendCallback(IAsyncResult ar)
        {
            try
            {
                Socket handler = (Socket)ar.AsyncState;
                int bytesSent = handler.EndSend(ar);
                handler.Shutdown(SocketShutdown.Both);
                handler.Close();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

问题是，当我从客户端发送图片到同步服务器，一切工作和服务器接收它，但如果我从同一个客户端发送图片到异步服务器，它不接收它。