could not change my serialport cable to null modem

i need time,may be 24 hour,reason works at my job

this is the full program
if u need i will attach the pic assembly program too,however i do not think it has any problem
#region Using directives
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;
#endregion

namespace SerialPort2Computer
{
public partial class Form1 : Form
{
SerialPort sp = new SerialPort();

public Form1()
{
InitializeComponent();
}

private void Form1_Load(object sender, EventArgs e)
{
sp.PortName="com2";
sp.BaudRate = 9600;
sp.DataBits = 8;
sp.Parity = Parity.None;
sp.StopBits = StopBits.One;
sp.Handshake = Handshake.None;
//
sp.Open();
sp.ReadTimeout = 500;
}

private void sendButton_Click(object sender, EventArgs e)
{
try
{
//write line to serial port
sp.WriteLine(textBox1.Text);
//clear the text box
textBox1.Text = "";
}
catch (System.Exception ex)
{
BaudRateLabel.Text = ex.Message;
}

}

private void ReadButton_Click(object sender, EventArgs e)
{
try
{
//clear the text box
textBox2.Text = "";
//read serial port and displayed the data in text box
textBox2.Text = sp.ReadLine();
}
catch (System.Exception ex)
{
BaudRateLabel.Text = ex.Message;
}
}

private void Form1_FormClosing(object sender, FormClosingEventArgs e)
{
MessageBox.Show("Do u want to Close the App");
sp.Close();
}

private void startCommButton_Click(object sender, EventArgs e)
{
startCommButton.Hide();
//
PortNameLabel.Text += " = " + sp.BaudRate.ToString();
BaudRateLabel.Text += " = " + sp.Parity.ToString();
DataBitsLabel.Text += " = " + sp.DataBits.ToString();
ReadTimeOutLabel.Text += " = " + sp.ReadTimeout.ToString();
ParityLabel.Text += " = " + sp.Parity.ToString();
StopBitsLabel.Text += " = " + sp.StopBits.ToString();
HandShakeLabel.Text += " = " + sp.Handshake.ToString();
//
sendButton.Show();
readButton.Show();
textBox1.Show();
textBox2.Show();
}

}
}