执行BeginSend时出现SocketException

Question

首先，这是我的代码：

public void requestLogin()
    {

        LoginRequest loginRequest = new LoginRequest { username = "matthew798", password = "test" };
        //var ip = IPAddress.Parse("127.0.0.1");
        //var ep = new IPEndPoint(ip, 4598);

        Socket client = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
        client.BeginConnect("127.0.0.1", 4598, new AsyncCallback(ConnectedCallback), client);
        connectDone.WaitOne();

        var sevenItems = new byte[] { 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20 };

        byte[] byteData = Serializer.GetByteArray<LoginRequest>(loginRequest);

        client.BeginSend(byteData, 0, byteData.Length, 0,
            new AsyncCallback(SendCallback), client);

        //Send(client, );
        sendDone.WaitOne();

        client.Shutdown(SocketShutdown.Both);

        client.Disconnect(true);
        if (client.Connected)
            Debug.Log("We're still connnected");
        else
            Debug.Log("We're disconnected");
        client.Close();
    }

    private void ConnectedCallback(IAsyncResult ar)
    {
        Socket client = (Socket)ar.AsyncState;

        client.EndConnect(ar);

        Debug.Log("Socket connected");

        connectDone.Set();
    }

    private static void Send(Socket client, String data)
    {
        // Convert the string data to byte data using ASCII encoding.
        byte[] byteData = Encoding.ASCII.GetBytes(data);

        // Begin sending the data to the remote device.
        client.BeginSend(byteData, 0, byteData.Length, 0,
            new AsyncCallback(SendCallback), client);
    }

    private static void SendCallback(IAsyncResult ar)
    {
        try
        {
            // Retrieve the socket from the state object.
            Socket client = (Socket)ar.AsyncState;

            // Complete sending the data to the remote device.
            int bytesSent = client.EndSend(ar);
            Console.WriteLine("Sent {0} bytes to server.", bytesSent);

            // Signal that all bytes have been sent.
            sendDone.Set();
        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }
    }

它是C＃中的套接字程序（它是统一项目的一部分）。当我调用requestLogin()函数时，它会连接并发送数据ONCE。我在TCP服务器模式下使用herculese-utility。按下任何子请求按钮会导致客户端连接到服务器，但不会发送任何内容并引发以下异常：

SocketException: A request to send or receive data was disallowed because the socket is not connected and (when sending on a datagram socket using a sendto call) no address was supplied