Is there a way to check socket available data, synchronously?

Question

i want to check the socket available data to read, before i call the receive() method. but it is not working. i think the way i am checking the socket available data is not correct. this is the code:

 private Socket _clientSocket;               //Client socket

  public Form1()
    {
        InitializeComponent();

        //Check for data available before calling Receive().
        if (_clientSocket.Poll(-1, SelectMode.SelectRead))
        {
            Receive();
        }


    }

it is giving me this error: Object reference not set to an instance of an object

what is the correct way to check socket available data to read? I am thinking some kind of events but i can't figure it out..

any help?

EDIT: Button for connection:

   private void BtnConnect_Click(object sender, EventArgs e)
    {
        try
        {
            string ip = TboxIP.Text;
            int port = int.Parse(TboxPort.Text);
            _clientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            // Connect to the  host
            _clientSocket.Connect(IPAddress.Parse(ip), port);

            if (SocketConnected(_clientSocket) == true)
            {
                lblStatus.Text = "Socket Connection Established .. ";
            }


        }
        catch (SocketException ex)
        {
            MessageBox.Show(ex.Message);
        }
    }

Answer 1

那是您的问题，您正在Form1构造函数中访问_clientSocket，并且尚未初始化。

Answer 2

Look documentation: Socket.Poll() if you set the microsecond number to negative like you did, it will wait forever for any kind of response.

Use waittime based on your testing, so it is not to