not reading data from serial port

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO.Ports;
using System.Timers;



namespace serialcomm
    
{ 
    public partial class Form1 : Form
    {
        SerialPort ComPort = new SerialPort();
        private Queue<byte> recievedData = new Queue<byte>();
        
        
        public Form1()
        { 
            InitializeComponent();
        }

        private void ports_Click(object sender, EventArgs e)
        { 
             
            
    string[] ArrayComPortsNames = null;
    int index = -1;
    string ComPortName = null;

    ArrayComPortsNames = SerialPort.GetPortNames();
    do
    {
        index += 1;
        comboBox1.Items.Add(ArrayComPortsNames[index]);
    }

    while (!((ArrayComPortsNames[index] == ComPortName)
                  || (index == ArrayComPortsNames.GetUpperBound(0))));
    Array.Sort(ArrayComPortsNames);

    //want to get first out
    if (index == ArrayComPortsNames.GetUpperBound(0))
    {
        ComPortName = ArrayComPortsNames[0];
    }
    comboBox1.Text = ArrayComPortsNames[0];
            // baud rate values

    cboBaudRate.Items.Add(300);
    cboBaudRate.Items.Add(600);
    cboBaudRate.Items.Add(1200);
    cboBaudRate.Items.Add(2400);
    cboBaudRate.Items.Add(9600);
    cboBaudRate.Items.Add(14400);
    cboBaudRate.Items.Add(19200);
    cboBaudRate.Items.Add(38400);
    cboBaudRate.Items.Add(57600);
    cboBaudRate.Items.Add(115200);
    cboBaudRate.Items.ToString();
    //get first item print in text
    cboBaudRate.Text = cboBaudRate.Items[0].ToString();
            // handshaking bits
    cboHandShaking.Items.Add("None");
    cboHandShaking.Items.Add("XOnXOff");
    cboHandShaking.Items.Add("RequestToSend");
    cboHandShaking.Items.Add("RequestToSendXOnXOff");
    cboHandShaking.Items.ToString();
    cboHandShaking.Text=cboHandShaking.Items[0].ToString();
            
           // data bits
            cboDataBits.Items.Add("7"); 
            cboDataBits.Items.Add("8");
            cboDataBits.Items.ToString();
            cboDataBits.Text = cboDataBits.Items[0].ToString();
            // stop bits
            cboStopBits.Items.Add("One");
            cboStopBits.Items.Add("OnePointFive");
            cboStopBits.Items.Add("Two");
            //get the first item print in the text
            cboStopBits.Text = cboStopBits.Items[0].ToString();

            //Parity 
            cboParity.Items.Add("None");
            cboParity.Items.Add("Even");
            cboParity.Items.Add("Mark");
            cboParity.Items.Add("Odd");
            cboParity.Items.Add("Space");
            cboParity.Text = cboParity.Items[0].ToString();
               
        }

       
        
        private void button1_Click(object sender, EventArgs e)
        { 
           

    if (button1.Text == "Closed")
    {
        button1.Text = "Open";
        ComPort.PortName = Convert.ToString(comboBox1.Text);
        ComPort.BaudRate = Convert.ToInt32(cboBaudRate.Text);
        ComPort.DataBits = Convert.ToInt32(cboDataBits.Text);
        ComPort.StopBits = (StopBits)Enum.Parse(typeof(StopBits), cboStopBits.Text);
        ComPort.Handshake = (Handshake)Enum.Parse(typeof(Handshake), cboHandShaking.Text);
        ComPort.Parity = (Parity)Enum.Parse(typeof(Parity), cboParity.Text);
        
        ComPort.Open();
        button1.BackColor = Color.Green;
    }
    else if (button1.Text == "Open")
    {
        button1.Text= "Closed";
        ComPort.Close();
        button1.BackColor = Color.Red;
    }
        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {

        }



        public class CommTimer
        {
            public System.Timers.Timer tmrComm = new System.Timers.Timer();
            public bool timedout = false;
            public  CommTimer()
            {
                timedout = false;
                tmrComm.AutoReset = false;
                tmrComm.Enabled = false;
                tmrComm.Interval = 1000; //default to 1 second
                tmrComm.Elapsed += new ElapsedEventHandler(OnTimedCommEvent);
            }

            public void OnTimedCommEvent(object source, ElapsedEventArgs e)
            {
                timedout = true;
                tmrComm.Stop();
            }

            public void Start(double timeoutperiod)
            {
                tmrComm.Interval = timeoutperiod;             //time to time out in milliseconds
                tmrComm.Stop();
                timedout = false;
                tmrComm.Start();
            }


        }



      

        private void button2_Click(object sender, EventArgs e)
        {
            string str = textBox1.Text;
            byte[] raw = new byte[textBox1.TextLength/2];
            for (int i = 0; i < raw.Length; i++)
            {
                raw[i] = Convert.ToByte(str.Substring(i * 2, 2), 16);



            }
           ComPort.Write(raw,0,raw.Length);
           ComPort.DataReceived += new SerialDataReceivedEventHandler(sp_DataReceived);

           
        }

        private void sp_DataReceived(object sender, SerialDataReceivedEventArgs e)
        {
             CommTimer tmrComm = new CommTimer();
            tmrComm.Start(4000);
             while ((ComPort.BytesToRead == 0) && (tmrComm.timedout == false))
            {
                Application.DoEvents();
            }

             int dataLength = ComPort.BytesToRead;
             byte[] data = new byte[dataLength / 2];
             string str = ComPort.ReadExisting();

             for (int i = 0; i < dataLength; i++)
             {
                 data[i] = Convert.ToByte(str.Substring(i * 2, 2), 16);
                 if (dataLength > 0)
                 {
                     textBox2.Text = Convert.ToString(data);
                 }

                tmrComm.tmrComm.Dispose();
                ComPort.DiscardInBuffer();
                ComPort.DiscardOutBuffer();
                ComPort.Close();

            }
        }
                        

        private void textBox2_TextChanged(object sender, EventArgs e)
        {

        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }
                                  
  }

}