GSM communication, cross threading

Question

I'm bit new in C# programming but somehow I managed to pickup a project that requires a great skill and knowledge with GSM (SMS) communication using serialPort.

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

namespace SMSget
{
    public partial class SMSLogPanel : UserControl
    {
        #region default constructor
        public SMSLogPanel()
        {
            InitializeComponent();
            serialPort1 = new SerialPort();
            serialPort1.DataBits = 8;
            serialPort1.DtrEnable = true;
            serialPort1.Encoding.Equals("iso-8859-1");
            serialPort1.Handshake = Handshake.RequestToSend;
            serialPort1.Parity = Parity.None;
            serialPort1.WriteTimeout = 300;
            serialPort1.StopBits = StopBits.One;
            checkLink();
        }
    #endregion
    #region checking communication and setting user controls...
    private void checkLink()
    {
        GetValues value = new GetValues();
        string com = value.getPort();
        int baud = value.getBaud();
        int timeot = value.getTimeout();
        serialPort1.PortName = com;
        serialPort1.BaudRate = baud;
        serialPort1.ReadTimeout = timeot;

        serialPort1.Open();
        if (serialPort1.IsOpen)
        {
            label1.Visible = true;
        }
        else
        {
            MessageBox.Show("Komunikacija sa modemom se ne može uspostaviti, molimo postavite novu konfiguraciju...!");
            this.Controls.Clear();
            SMSConfigPanel cfg = new SMSConfigPanel();
            cfg.Show();
            this.Controls.Add(cfg);
        }
        serialPort1.Close();
    }
    #endregion
    #region setiranje timer-a...
    private void timer1_Tick(object sender, EventArgs e)
    {
        timer1.Stop();
        execCommand();
        timer1.Start();
    }
    #endregion
    #region seting handler and executing AT commands
    public void execCommand()
    {
        serialPort1.DataReceived += new SerialDataReceivedEventHandler(getResponse);
        serialPort1.Open();
        //prazni se buffer da se ne pokupe neke vrijednosti koje ne trebaju...
        serialPort1.DiscardInBuffer();

        if (!serialPort1.IsOpen)
        {
            MessageBox.Show("Modem nije spojen, molimo provjerite konfiguraciju...!");
            timer1.Stop();
        }
        serialPort1.Write("AT+CMGF=1" + (char)(13));
        serialPort1.Write("AT+CMGL=\"ALL\"" + (char)(13));
    }
    public void getResponse(object sender, SerialDataReceivedEventArgs e)
    {
        SerialPort serPort = (SerialPort)sender;
        string input = serPort.ReadExisting();
        if (input.Contains("ERROR"))
        {
            //textBox2.Text = "";
        }
        else if (input.Contains("+CMTI:"))
        {
            serialPort1.Write("AT+CMGF=1" + (char)(13));
            serialPort1.Write("AT+CMGL=\"ALL\"" + (char)(13));
        }
        else if (input.Contains("+CMGL:"))
        {
            textBox1.Text = input;
        }
        else
        {
            return;
        }
        serialPort1.Close();
    }
    #endregion
}

}

I think that somehow I managed to create bugs in these areas (not opening/closing serialPort1 ports, input data in getResponse(object sender, SerialDataReceivedEventArgs e) which uses separate thread cannot be passed into textBox1 due to cross thread issue..., and probably wrong AT command for reading UNREADED MESSAGES that has been received...)

If anyone can help me with this, I would be very grateful...

Thank you and best regards.

you are having a cross thread exception? – Ehsan Aug 19 '13 at 17:29 — Ehsan, Aug 19 '13 at 17:29

score 0 · Answer 1 · answered Aug 19 '13 at 17:30

0

Reason for Cross thread exception:

You are trying to update GUI element on a thread other then the one on which it was created. it is not allowed.

Solution:

To avoid cross thread exception. You should update your code like this

this.Invoke((MethodInvoker) delegate
    {
        // update your textbox here

    });

answered Aug 19 '13 at 17:30

Ehsan

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I'll try it, but can you advise me if opening and closing serialPort1 is done properly, because it confuses me... I'm not sure if I setup serialPort1.Open() and serialPort1.Close() at the right place... – dovla110010101 Aug 19 '13 at 18:41

score 0 · Answer 2 · edited May 23 '17 at 10:25

serialPort1.Write("AT+CMGF=1" + (char)(13));
serialPort1.Write("AT+CMGL=\"ALL\"" + (char)(13));

This is not correct. You MUST read and parse the response given back from the modem after each command, e.g. something like

serialPort1.Write("AT+CMGF=1" + (char)(13));
waitForFinalResponse(serialPort1);
serialPort1.Write("AT+CMGL=\"ALL\"" + (char)(13));
waitForFinalResponse(serialPort1);

or possibly combine serialPort1.Write and waitForFinalResponse into a sendATCommand function. See also this and this answer for more details.

GSM communication, cross threading

2 Answers2