SMS connecting to a phone from C# and getting a response

I wrote code to send an SMS using my GSM phone which is attached to the computer through COM port. The code is below.

The problem is I do see that it is in the outbox of the phone and it actually appears to have been sent, but when I contact the recipient they say that I have not received the message.

I test the phone, and I create and send a message using only the phone and it works perfectly. However, when I do this with my code, it APPEARS to have been sent, and I am getting all the correct AT COMMAND responses from the phone, but the message is actually NOT sent.

Here is the code:

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.Threading;
using System.IO.Ports;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        SerialPort serialPort1;
        int m_iTxtMsgState = 0;
        const int NUM_MESSAGE_STATES = 4;
        const string RESERVED_COM_1 = "COM1";
        const string RESERVED_COM_4 = "COM4";

        public Form1()
        {
            InitializeComponent();

            this.Closing += new CancelEventHandler(Form1_Closing);
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            serialPort1 = new SerialPort(GetUSBComPort());

            if (serialPort1.IsOpen)
            {
                serialPort1.Close();
            }

            serialPort1.Open();

            //ThreadStart myThreadDelegate = new ThreadStart(ReceiveAndOutput);
            //Thread myThread = new Thread(myThreadDelegate);
            //myThread.Start();

            this.serialPort1.DataReceived += new SerialDataReceivedEventHandler(sp_DataReceived);
        }

        private void Form1_Closing(object sender, System.ComponentModel.CancelEventArgs e)
        {
            serialPort1.Close();
        }

        private void SendLine(string sLine)
        {
            serialPort1.Write(sLine);
            sLine = sLine.Replace("\u001A", "");
            consoleOut.Text += sLine;
        }

        public void DoWork()
        {
            ProcessMessageState();
        }

        public void ProcessMessageState()
        {
            switch (m_iTxtMsgState)
            {
                case 0:
                    m_iTxtMsgState = 1;
                    SendLine("AT\r\n");  //NOTE: SendLine must be the last thing called in all of these!
                break;

                case 1:
                    m_iTxtMsgState = 2;
                    SendLine("AT+CMGF=1\r\n");

                break;

                case 2:
                    m_iTxtMsgState = 3;
                    SendLine("AT+CMGW=" + Convert.ToChar(34) + "+9737387467" + Convert.ToChar(34) + "\r\n");
                break;

                case 3:
                    m_iTxtMsgState = 4;
                    SendLine("A simple demo of SMS text messaging." + Convert.ToChar(26));
                break;

                case 4:
                    m_iTxtMsgState = 5;

                break;

                case 5:
                    m_iTxtMsgState = NUM_MESSAGE_STATES;
                break;
            }
        }

        private string GetStoredSMSID()
        {开发者_如何学运维
            return null;
        }

        /* //I don't think this part does anything
        private void serialPort1_DataReceived_1(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
        {
            string response = serialPort1.ReadLine();
            this.BeginInvoke(new MethodInvoker(() => textBox1.AppendText(response + "\r\n")));
        }
        */
        void sp_DataReceived(object sender, SerialDataReceivedEventArgs e)
        {
            try
            {
                Thread.Sleep(500);

                char[] msg;
                msg = new char[613];
                int iNumToRead = serialPort1.BytesToRead;

                serialPort1.Read(msg, 0, iNumToRead);

                string response = new string(msg);

                this.BeginInvoke(new MethodInvoker(() => textBox1.AppendText(response + "\r\n")));
                serialPort1.DiscardInBuffer();

                if (m_iTxtMsgState == 4)
                {
                    int pos_cmgw = response.IndexOf("+CMGW:");
                    string cmgw_num = response.Substring(pos_cmgw + 7, 4);
                    SendLine("AT+CMSS=" + cmgw_num + "\r\n");
                    //stop listening to messages received
                }

                if (m_iTxtMsgState < NUM_MESSAGE_STATES)
                {
                    ProcessMessageState();
                }
            }
            catch
            { }
        }

        private void button1_Click(object sender, EventArgs e)
        {
            m_iTxtMsgState = 0;
            DoWork();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            string[] sPorts = SerialPort.GetPortNames();
            foreach (string port in sPorts)
            {
                consoleOut.Text += port + "\r\n";
            }
        }

        private string GetUSBComPort()
        {
            string[] sPorts = SerialPort.GetPortNames();
            foreach (string port in sPorts)
            {
                if (port != RESERVED_COM_1
                    && port != RESERVED_COM_4)
                {
                    return port;
                }
            }

            return null;
        }
    }

---

This is my code that works (tested) with U9 Telia cellular modem:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;
using System.Diagnostics;
using System.Configuration;

using UsbEject.Library;
using Utils;

namespace Hardware
{
    public class TeliaModem : IDisposable
    {
        public delegate void NewSmsHandler(InboundSMS sms);
        public event NewSmsHandler OnNewSMS;

        #region private data
        System.IO.Ports.SerialPort modemPort;

        Timeouter _lastModemKeepAlive;

        private delegate void DataReceivedDelegate();
        private DataReceivedDelegate dataReceivedDelegate;

        Queue<OutboundSMS> _outSmses = new Queue<OutboundSMS>();

        enum ModemState
        {
            Error = -1, NotInitialized, PowerUp, Initializing, Idle,
            SendingSMS, KeepAliveAwaitingResponse
        };

        Timeouter ModemStateTimeouter = new Timeouter(timeout_s: 10, autoReset: false);
        ModemState _modemState = ModemState.NotInitialized;
        ModemState CurrentModemState
        {
            get
            {
                return _modemState;
            }
            set
            {
                _modemState = value;
                ModemStateTimeouter.Reset();
                NihLog.Write(NihLog.Level.Debug, "State changed to: " + value.ToString());
            }
        }

        private System.Windows.Forms.Control _mainThreadOwnder;
        #endregion

        public TeliaModem(System.Windows.Forms.Control mainThreadOwnder)
        {
            _mainThreadOwnder = mainThreadOwnder;

            dataReceivedDelegate = new DataReceivedDelegate(OnDataReceived);
        }

        public void SendSMS(string phone, string text)
        {
            _outSmses.Enqueue(new OutboundSMS(phone, text));
            HeartBeat();
        }

        private void SendSmsNow()
        {
            OutboundSMS sms = _outSmses.Peek();
            sms.Attempt++;
            if (sms.Attempt > sms.MaxTries)
            {
                NihLog.Write(NihLog.Level.Error, "Failure to send after " + sms.MaxTries + " tries");
                _outSmses.Dequeue();
                return;
            }

            NihLog.Write(NihLog.Level.Info, "Sending SMS: " + sms.ToString());
            WriteToModem("AT+CMGS=\"" + sms.Destination + "\"\r");
            System.Threading.Thread.Sleep(500);
            WriteToModem(sms.Text);

            byte[] buffer = new byte[1];
            buffer[0] = 26; // ^Z
            modemPort.Write(buffer, offset:0, count:1);

            CurrentModemState = ModemState.SendingSMS;
        }

        public void Dispose()
        {
            UninitModem();
        }

        public void HeartBeat()
        {
            if (CurrentModemState == ModemState.NotInitialized)
            {
                TryInitModem();
                return;
            }

            if (IsTransitionalState(CurrentModemState) && ModemStateTimeouter.IsTimedOut())
            {
                NihLog.Write(NihLog.Level.Error, "Modem error. Timed out during " + CurrentModemState);
                CurrentModemState = ModemState.Error;
                return;
            }

            if (CurrentModemState == ModemState.Idle && _lastModemKeepAlive.IsTimedOut())
            {
                // Send keepalive
                WriteToModem("AT\r");
                CurrentModemState = ModemState.KeepAliveAwaitingResponse;
                return;
            }

            if (CurrentModemState == ModemState.Error)
            {
                NihLog.Write(NihLog.Level.Debug, "Reenumerating modem...");
                UninitModem();
                return;
            }

            if (_outSmses.Count != 0 && CurrentModemState == ModemState.Idle)
            {
                SendSmsNow();
                return;
            }
        }

        private string pendingData;
        private void OnDataReceived()
        {
            // Called in the main thread

            string nowWhat = modemPort.ReadExisting();
            pendingData += nowWhat;
            string[] lines = pendingData.Split(new string[] { "\r\n" }, StringSplitOptions.None);
            if (lines.Length == 0)
            {
                pendingData = string.Empty;
                return;
            }
            else
            {
                pendingData = lines[lines.Length - 1];
            }

            // This happens in main thread.
            for (int i = 0; i < lines.Length - 1; i++)
            {
                string line = lines[i];

                if (line.Length >= 5 && line.Substring(0, 5) == "+CMT:")
                {
                    // s+= read one more line
                    if (i == lines.Length - 1) // no next line
                    {
                        pendingData = line + "\r\n" + pendingData; // unread the line
                        continue;
                    }
                    string line2 = lines[++i];
                    NihLog.Write(NihLog.Level.Debug, "RX " + line);
                    NihLog.Write(NihLog.Level.Debug, "RX " + line2);
                    InboundSMS sms = new InboundSMS();
                    sms.ParseCMT(line, line2);
                    if(OnNewSMS != null)
                        OnNewSMS(sms);
                }
                else   // Not a composite
                    NihLog.Write(NihLog.Level.Debug, "RX " + line);

                if (line == "OK")
                {
                    OnModemResponse(true);
                }
                else if (line == "ERROR")
                {
                    OnModemResponse(false);
                    NihLog.Write(NihLog.Level.Error, "Modem error");
                }
            }
        }

        private void ProcessSmsResult(bool ok)
        {
            if (!ok)
            {
                OutboundSMS sms = _outSmses.Peek();
                if (sms.Attempt < sms.MaxTries)
                {
                    NihLog.Write(NihLog.Level.Info, "Retrying sms...");
                    return;
                }

                NihLog.Write(NihLog.Level.Error, "Failed to send SMS: " + sms.ToString());
            }

            _outSmses.Dequeue();
        }

        private void OnModemResponse(bool ok)
        {
            if (CurrentModemState == ModemState.SendingSMS)
                ProcessSmsResult(ok);

            if (!ok)
            {
                NihLog.Write(NihLog.Level.Error, "Error during state " + CurrentModemState.ToString());
                CurrentModemState = ModemState.Error;
                return;
            }

            switch (CurrentModemState)
            {
                case ModemState.NotInitialized:
                    return;

                case ModemState.PowerUp:
                    WriteToModem("ATE0;+CMGF=1;+CSCS=\"IRA\";+CNMI=1,2\r");
                    CurrentModemState = ModemState.Initializing;
                    break;

                case ModemState.Initializing:
                case ModemState.SendingSMS:
                case ModemState.KeepAliveAwaitingResponse:
                    CurrentModemState = ModemState.Idle;
                    break;
            }
        }

        private void CloseU9TelitNativeApp()
        {
            bool doneSomething;

            do
            {
                doneSomething = false;

                Process[] processes = Process.GetProcessesByName("wirelesscard");
                foreach (Process p in processes)
                {
                    p.CloseMainWindow();
                    doneSomething = true;
                    NihLog.Write(NihLog.Level.Info, "Killed native U9 app");
                    System.Threading.Thread.Sleep(1000); // Will not wait if no native app is started
                }
            } while (doneSomething);
        }

        void WriteToModem(string s)
        {
            modemPort.Write(s);
            NihLog.Write(NihLog.Level.Debug, "TX " + s);
        }

        void UninitModem()
        {
            if (modemPort != null)
                modemPort.Dispose();
            modemPort = null;
            CurrentModemState = ModemState.NotInitialized;
        }

        private bool IsTransitionalState(ModemState ms)
        {
            return ms == ModemState.Initializing
                || ms == ModemState.SendingSMS
                || ms == ModemState.PowerUp
                || ms == ModemState.KeepAliveAwaitingResponse;
        }

        Timeouter _initFailureTimeout = 
            new Timeouter(timeout_s: 10, autoReset:false, timedOut:true);

        void TryInitModem()
        {
            // Try pistoning the modem with higher frequency. This does no harm (such as redundant logging)
            PrepareU9Modem();   // Will do nothing if modem is okay

            if (!_initFailureTimeout.IsTimedOut())
                return; // Don't try too frequently

            if (modemPort != null)
                return;

            const string modemPortName = "Basecom HS-USB NMEA 9000";
            const int speed = 115200;

            string portName = Hardware.Misc.SerialPortFromFriendlyName(modemPortName);
            if (portName == null)
            {
                NihLog.Write(NihLog.Level.Error, "Modem not found (yet). ");
                _initFailureTimeout.Reset();
                return;
            }

            NihLog.Write(NihLog.Level.Info, string.Format("Found modem port \"{0}\" at {1}", modemPortName, portName));
            modemPort = new System.IO.Ports.SerialPort(portName, speed);
            modemPort.ReadTimeout = 3000;
            modemPort.NewLine = "\r\n";

            modemPort.Open();

            modemPort.DiscardInBuffer();
            modemPort.DataReceived += new System.IO.Ports.SerialDataReceivedEventHandler(delegate { _mainThreadOwnder.Invoke(dataReceivedDelegate); });  // called in different thread!

            _lastModemKeepAlive = new Timeouter(60, true);

            WriteToModem("AT+CFUN=1\r");
            CurrentModemState = ModemState.PowerUp;
        }

        void CheatU9Telit()
        {
            // U9 telit appears as USB CDrom on the bus, until disk eject is sent.
            // Then, it reappears as normal stuff.

            VolumeDeviceClass volumeDeviceClass = new VolumeDeviceClass();
            foreach (Volume device in volumeDeviceClass.Devices)
            {
                if (device.FriendlyName == "PCL HSUPA Modem USB Device")
                {
                    NihLog.Write(NihLog.Level.Info, "Trying to initialize: " + device.FriendlyName);
                    device.EjectCDRomNoUI();
                }
            }
        }

        void PrepareU9Modem()
        {
            CloseU9TelitNativeApp(); // Closes the autorun native app
            CheatU9Telit();
        }
    }

    public class OutboundSMS
    {
        public string Destination;
        public string Text;
        public int MaxTries;
        public int Attempt = 0;

        public OutboundSMS(string dest, string txt)
        {
            Destination = dest;
            Text = txt;
            MaxTries = 3;
        }

        override public string ToString()
        {
            if(Attempt > 1)
                return string.Format("\"{0}\" to {1}, attempt {2}", 
                    Text, Destination, Attempt);
            else
                return string.Format("\"{0}\" to {1}",
                    Text, Destination);
        }
    }

    public class InboundSMS
    {
        public string SourcePhone;
        public DateTime ReceiveTime;
        public string Text;

        public void ParseCMT(string line1, string line2)
        {
            string[] fields = line1.Split(new char[] { ',', ' ', '/', ':', '"' });
            if (fields.Length < 12)
                throw new ApplicationException("CMT message too short. Expected 2 fields");

            SourcePhone = fields[3];
            ReceiveTime = DateTime.Parse("20" + fields[7] + "-" + fields[8] + "-" + fields[9] + " " + fields[10] + ":" + fields[11] + ":" + fields[12].Substring(0, 2));   //test carefully
            Text = line2;
        }
    };
}

Usage example in a winforms application:

Hardware.TeliaModem _modem;

public Form1()
{
    InitializeComponent();

    _modem = new Hardware.TeliaModem(this);

    _modem.OnNewSMS += new Hardware.TeliaModem.NewSmsHandler(ProcessNewSMS);

        _timer.Interval = 1000; // milliseconds
        _timer.Tick += new EventHandler(OnTimerTick);
        _timer.Start();
}

To send an SMS:

        _modem.SendSMS(sms.SourcePhone, "Aircon is now " + BoolToString.ON_OFF(_aircon.On));

On timer event, once every second:

private void OnTimerTick(object o, EventArgs e)
{
    _modem.HeartBeat();
}

This is registered as Winforms timer handler, so that modem will not have a thread.

Some utility classes used:

namespace Utils
{
    public class StopWatch
    {
        protected DateTime _resetTime;

        public StopWatch() { Reset(); }
        public void Reset() { _resetTime = DateTime.Now; }
        public double TotalSeconds { get { return (DateTime.Now - _resetTime).TotalSeconds; } }
        public TimeSpan Time { get { return DateTime.Now - _resetTime; } }
    };

    public class Timeouter : StopWatch
    {
        private bool _autoReset;
        private double _timeout_s;

        public Timeouter(double timeout_s, bool autoReset, bool timedOut = false)
        {
            _timeout_s = timeout_s;
            _autoReset = autoReset;

            if (timedOut)
                _resetTime -= TimeSpan.FromSeconds(_timeout_s + 1);  // This is surely timed out, as requested
        }

        public bool IsTimedOut()
        {
            if (_timeout_s == double.PositiveInfinity)
                return false;

            bool timedout = this.TotalSeconds >= _timeout_s;

            if (timedout && _autoReset)
                Reset();

            return timedout;
        }

        public void Reset(double timeout_s) { _timeout_s = timeout_s; Reset(); }
        public double TimeLeft { get { return _timeout_s - TotalSeconds; } }
    }
}

I implemented this in order to turn on air conditioner with SMS (yeah, I live in a hot country). It works. Please feel free to use any of this code.

Enjoy.

---

Microsoft provides a pretty decent VB.Net example in a KB article "How to access serial and parallel ports by using Visual Basic .NET". I'm not sure what your phone returns, however, if you change the buffer loop in the example, you can at least print out the reply:

MSComm1.Output = "AT" & Chr(13)
Console.WriteLine("Send the attention command to the modem.")
Console.WriteLine("Wait for the data to come back to the serial port...")
' Make sure that the modem responds with "OK".
' Wait for the data to come back to the serial port.
Do
    Buffer = Buffer & MSComm1.Input
    Console.WriteLine("Found: {0}", Buffer)
Loop Until InStr(Buffer, "OK" & vbCrLf)

---

GSMComm is a C# library that will allow you to easily interact with a GSM mobile in text or PDU mode. (The site also has a bunch of testing utilities)

---

Working with GSM modem to send SMS has never been a good idea as such. Here's a checklist to make sure your SMS is sent out properly.

• You are sending the SMS in text mode. Try sending it in PDU mode.
• Try this library http://phonemanager.codeplex.com/
• Do you change SMSC number before sending out the SMS, if so make sure the SMSC is correct.
• Also make sure your SIM card has enough credits to let you send outbound SMS.
• Check the network status especially when you're sending out SMS from your program. This might be a problem.

I recommend you checkout the Lite edition of NowSMS gateway that comes for free and lets you work with GSM modem very continently. NowSMS will give you api abstraction over a GSM modem connection, so you wil just need to call the Http Api of NowSMS gateway, rest will be taken care by the NowSMS gateway.

Above all this, if your end-users are going to remain internet connected while using your application or if your application is web-based and hosted over internet, I strongly recoomend to do away with GSM modem option and opt-in for reliable Http SMS gateway service providers.