read messages from multiple sim

Thank you for ur responds..
in my code i have two com ports.. when i run my code the first device read the messeges correctly and give the count also read the second device messages..
my code is
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 Microsoft.VisualBasic;
using System.Net;
using System.IO.Ports;
using System.Security.Permissions;

namespace Eben_Longcode_Manager
{
public partial class main : Form
{
public main()
{
InitializeComponent();
}
#region Public Variables
public int baurd_rate, thread_exit = 0, msg_read = 0, msg_rcvd = 0, msg_read1 = 0;

public string port_name;
string msg1,
mob = "", mob1 = "";
bool isbgw = true;
bool isbgw1 = true;
SerialPort port = new SerialPort();
Eben_Longcode_Manager.Classes.clsSMS objclsSMS = new Eben_Longcode_Manager.Classes.clsSMS();
Eben_Longcode_Manager.Classes.ShortMessageCollection objShortMessageCollection = new Eben_Longcode_Manager.Classes.ShortMessageCollection();
#endregion
private void main_Load(object sender, EventArgs e)
{
#region Display all available COM Ports
try
{
string[] ports = SerialPort.GetPortNames();
foreach (string port in ports) // Add all port names to the combo box:
{
this.cmb_port.Items.Add(port);
this.cmb_port1.Items.Add(port);
this.cmb_port2.Items.Add(port);
}
}
catch (Exception)
{

throw;
}

#endregion
}

private void btn_connect_Click(object sender, EventArgs e)
{
try
{
port_name = cmb_port.Text;
baurd_rate = Convert.ToInt32(cmb_baurd.Text);
this.port = objclsSMS.OpenPort(port_name, baurd_rate, Convert.ToInt32("8"), Convert.ToInt32("300"), Convert.ToInt32("300"));
btn_start.Enabled = true; //enable start button
btn_disconnect.Enabled = true; //enable disconnect button
btn_connect.Enabled = false; //disable connect button
if (mob == "")
setnumber();
lbl_status.Text = "Device connected at port " + port_name;
}
catch (Exception)
{

throw;
}

}

private void btn_Connect1_Click(object sender, EventArgs e)
{
try
{
port_name = cmb_port1.Text;
baurd_rate = Convert.ToInt32(cmb_baurd1.Text);
this.port = objclsSMS.OpenPort(port_name, baurd_rate, Convert.ToInt32("8"), Convert.ToInt32("300"), Convert.ToInt32("300"));
btn_Start1.Enabled = true;
btn_Disconnect1.Enabled = true;
btn_Connect1.Enabled = false;
if (mob1 == "")
setnumber();
lbl_status1.Text = "Device connected at port " + port_name;
}
catch (Exception)
{

throw;
}

}
public void setnumber()
{
try
{
string myValue = Interaction.InputBox("Please provide the mobile number", "Mobile Number", mob, 100, 100);// If user has clicked Cancel, set myValue to defaultValue
if (myValue == "")
myValue = mob;
else
mob = myValue;
if (tbdevice1.Focus())
{
lbl_number.Text = mob;
}
if (tbdevice2.Focus())
{
lbl_devicenumber.Text = mob;