C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO.Ports;

using RS232;

namespace RemoteCFG
{
    public class RemoteConfiguration
    {
        SerialPort serialPort;
        RS232Comm rs232Comm = new RS232Comm();
        Object lockingObj = new object();

        public RemoteConfiguration()
        {
            
        }

        public string strMessage { get; set; }
        public string cfgNumber { get; set; }
        public string vloValue { get; set; }
        public string atcValue { get; set; }
            

        public List<string> EnumerateComPorts()
        {
            return rs232Comm.GetAvailableComPorts();
        }

        public int OpenPort(string comPort)
        {
            serialPort = rs232Comm.OpenPort(comPort);
            serialPort.DataReceived +=new SerialDataReceivedEventHandler(serialPort_DataReceived);

            if (serialPort != null)
                return 1;
            else
                return 0;
        }

        public int ClosePort()
        {
            try
            {
                serialPort.Close();
                return 1;
            }
            catch (Exception ex)
            {
                return 0;
            }
        }

        void serialPort_DataReceived(object sender, SerialDataReceivedEventArgs e)
        {
            SerialPort sp = (SerialPort)sender;
            string inData = sp.ReadExisting().Trim();
            strMessage = inData;

            switch (inData)
            {
                case "PLC": SendMsg("OK"); break;
                case "CFG": ValidateCFG(); break;
                case "OFF": serialPort.Close(); break;
                case "VLO": GetVLO(); break;
                case "ATC": GetATC(); break;
                default: System.Diagnostics.Debug.WriteLine(strMessage); break;
            }
        }

        private void GetATC()
        {
            if (atcValue != null && atcValue != string.Empty)
            {
                int value = 0;

                if (int.TryParse(atcValue, out value))
                {
                    if (value >= 0 || value <= 99)
                    {
                        SendMsg(atcValue);
                    }
                }
            }
        }

        private void GetVLO()
        {
            if (vloValue != null && vloValue != string.Empty)
            {
                int value = 0;

                if (int.TryParse(vloValue, out value))
                {
                    if (value >= 60 || value <= 120)
                    {
                        SendMsg(vloValue);
                    }
                }
            }
        }

        private void ValidateCFG()
        {
            if (cfgNumber != null && cfgNumber != null && cfgNumber != string.Empty)
            {
                if (cfgNumber.Length == 9) 
                {
                    try
                    {
                        int Num = 0;

                        if (int.TryParse(cfgNumber.Substring(0, 3), out Num))
                        {
                            int errorCounter = System.Text.RegularExpressions.Regex.Matches(cfgNumber.Substring(3, 1), @"[a-zA-Z]").Count;

                            if (errorCounter == 1) 
                            {
                                if (int.TryParse(cfgNumber.Substring(4), out Num))
                                    SendMsg(cfgNumber);
                            }
                        }
                    }
                    catch
                    {
                    }
                }
            }
        }

        public int GetCFG(ref string configNumber)
        {
            int status = 0;

            try
            {
                SendMsg("CFG");
                configNumber = strMessage;
            }
            catch
            {
            }

            return status;
        }

        int GetDynData(string[] dynamicData)
        {
            int status = 0;
            return status;
        }

        public int SendMsg(string msg)
        {
            int status = 0;
            
            serialPort.Write(msg + "\r");

            return status;
        }
    }
}

serialPort = new SerialPort(comPortName, 9600, Parity.Even, 7, StopBits.One);
serialPort.Handshake = Handshake.XOnXOff;