Introduction
When do you want to send SMS via applications? There could be plethora of use cases for this. The simplest one is to validate a mobile number, and some of the complicated ones could involve sending an SMS after a huge workflow is complete or gone wrong. Let's find out ways to send SMS using C#/VB.NET.
Sending SMS
What are the ways in which one can send SMS?
- Using a GSM modem:
- Better when one wants to implement offline applications and a very small number of SMS go every minute, usually few 10s.
- Using web service:
- Better when it is an online application and a very few number of SMS go every minute, usually few 10s.
- Using endpoints given by service the provider:
- Better when the number of SMS exceeds a few 100s per minute. Service provider demands a commitment of at least 100,000 SMS per month.
Sending SMS via a webservice or endpoints is simplest. In contrast, sending SMS via GSM modem has a few additional steps to take care of. Let's understand each in detail.
Sending SMS via GSM modem
- First, find the best GSM modem that suits the needs. Specifications are available here.
- Understand the AT Command set required to communicate with the modem.
- Connect the modem to the computer according to the setup guide specified in the manual provided with the GSM modem. Sample connection details of the Maestro 20/100 modem can be found here. The connection settings explained are common for most GSM modems.
- Create a new Windows application or Web Application.
- Add a new class file with the name SMSCOMMS.
- Copy and paste the code given below into the class.
Coding with VB.NET
If you are using VB.NET for coding the application, you can use the class shared by Jeanred. Details are as follows:
Option Explicit On
Imports System
Imports System.Threading
Imports System.ComponentModel
Imports System.IO.PortsPublic Class SMSCOMMS
Private WithEvents SMSPort As SerialPort
Private SMSThread As Thread
Private ReadThread As Thread
Shared _Continue As Boolean = False
Shared _ContSMS As Boolean = False
Private _Wait As Boolean = False
Shared _ReadPort As Boolean = False
Public Event Sending(ByVal Done As Boolean)
Public Event DataReceived(ByVal Message As String)
Public Sub New(ByRef COMMPORT As String)
SMSPort = New SerialPort
With SMSPort
.PortName = COMMPORT
.BaudRate = 9600
.Parity = Parity.None
.DataBits = 8
.StopBits = StopBits.One
.Handshake = Handshake.RequestToSend
.DtrEnable = True
.RtsEnable = True
.NewLine = vbCrLf
End With
ReadThread = New Thread(AddressOf ReadPort)
End Sub
Public Function SendSMS(ByVal CellNumber As String,
ByVal SMSMessage As String) As Boolean
Dim MyMessage As String = Nothing
If SMSMessage.Length <= 160 Then
MyMessage = SMSMessage
Else
MyMessage = Mid(SMSMessage, 1, 160)
End If
If IsOpen = True Then
SMSPort.WriteLine("AT+CMGS=" & CellNumber & vbCr)
_ContSMS = False
SMSPort.WriteLine(MyMessage & vbCrLf & Chr(26))
_Continue = False
RaiseEvent Sending(False)
End If
End Function
Private Sub ReadPort()
Dim SerialIn As String = Nothing
Dim RXBuffer(SMSPort.ReadBufferSize) As Byte
Dim SMSMessage As String = Nothing
Dim Strpos As Integer = 0
Dim TmpStr As String = Nothing
While SMSPort.IsOpen = True
If (SMSPort.BytesToRead <> 0) And (
SMSPort.IsOpen = True) Then
While SMSPort.BytesToRead <> 0
SMSPort.Read(RXBuffer, 0, SMSPort.ReadBufferSize)
SerialIn =
SerialIn & System.Text.Encoding.ASCII.GetString(
RXBuffer)
If SerialIn.Contains(">") = True Then
_ContSMS = True
End If
If SerialIn.Contains("+CMGS:") = True Then
_Continue = True
RaiseEvent Sending(True)
_Wait = False
SerialIn = String.Empty
ReDim RXBuffer(SMSPort.ReadBufferSize)
End If
End While
RaiseEvent DataReceived(SerialIn)
SerialIn = String.Empty
ReDim RXBuffer(SMSPort.ReadBufferSize)
End If
End While
End Sub
Public ReadOnly Property IsOpen() As Boolean
Get
If SMSPort.IsOpen = True Then
IsOpen = True
Else
IsOpen = False
End If
End Get
End Property
Public Sub Open()
If IsOpen = False Then
SMSPort.Open()
ReadThread.Start()
End If
End Sub
Public Sub Close()
If IsOpen = True Then
SMSPort.Close()
End If
End Sub
End Class
The above class exposes three functions: Open, SendSMS and Close. While creating the instance of the class, provide the port to which the modem is connected. In a Windows application, follow the steps below:
SMSEngine = New SMSCOMMS("COM1")
SMSEngine.Open()
SMSEngine.SendSMS("919888888888","SMS Testing")
SMSEngine.Close()
Coding with C#
The C# implementation of the code is as follows:
using System;
using System.Threading;
using System.ComponentModel;
using System.IO.Ports;
public class SMSCOMMS
{
private SerialPort SMSPort;
private Thread SMSThread;
private Thread ReadThread;
public static bool _Continue = false;
public static bool _ContSMS = false;
private bool _Wait = false;
public static bool _ReadPort = false;
public delegate void SendingEventHandler(bool Done);
public event SendingEventHandler Sending;
public delegate void DataReceivedEventHandler(string Message);
public event DataReceivedEventHandler DataReceived;
public SMSCOMMS(ref string COMMPORT)
{
SMSPort = new SerialPort();
SMSPort.PortName = COMMPORT;
SMSPort.BaudRate = 9600;
SMSPort.Parity = Parity.None;
SMSPort.DataBits = 8;
SMSPort.StopBits = StopBits.One;
SMSPort.Handshake = Handshake.RequestToSend;
SMSPort.DtrEnable = true;
SMSPort.RtsEnable = true;
SMSPort.NewLine = System.Environment.NewLine;
ReadThread = new Thread(
new System.Threading.ThreadStart(ReadPort));
}
public bool SendSMS(string CellNumber, string SMSMessage)
{
string MyMessage = null;
if (SMSMessage.Length <= 160)
MyMessage = SMSMessage;
else
MyMessage = SMSMessage.Substring(0, 160);
if (IsOpen == true)
{
SMSPort.WriteLine("AT+CMGS=" + CellNumber + "r");
_ContSMS = false;
SMSPort.WriteLine(
MyMessage + System.Environment.NewLine + (char)(26));
_Continue = false;
if (Sending != null)
Sending(false);
}
return false;
}
private void ReadPort()
{
string SerialIn = null;
byte[] RXBuffer = new byte[SMSPort.ReadBufferSize + 1];
string SMSMessage = null;
int Strpos = 0;
string TmpStr = null;
while (SMSPort.IsOpen == true)
{
if ((SMSPort.BytesToRead != 0) & (SMSPort.IsOpen == true))
{
while (SMSPort.BytesToRead != 0)
{
SMSPort.Read(RXBuffer, 0, SMSPort.ReadBufferSize);
SerialIn =
SerialIn + System.Text.Encoding.ASCII.GetString(
RXBuffer);
if (SerialIn.Contains(">") == true)
{
_ContSMS = true;
}
if (SerialIn.Contains("+CMGS:") == true)
{
_Continue = true;
if (Sending != null)
Sending(true);
_Wait = false;
SerialIn = string.Empty;
RXBuffer = new byte[SMSPort.ReadBufferSize + 1];
}
}
if (DataReceived != null)
DataReceived(SerialIn);
SerialIn = string.Empty;
RXBuffer = new byte[SMSPort.ReadBufferSize + 1];
}
}
}
public bool SendSMS(string CellNumber, string SMSMessage)
{
string MyMessage = null;
if (SMSMessage.Length <= 160)
{
MyMessage = SMSMessage;
}
else
{
MyMessage = SMSMessage.Substring(0, 160);
}
if (IsOpen == true)
{
SMSPort.WriteLine("AT+CMGS=" + CellNumber + "r");
_ContSMS = false;
SMSPort.WriteLine(
MyMessage + System.Environment.NewLine + (char)(26));
_Continue = false;
if (Sending != null)
Sending(false);
}
return false;
}
public void Open()
{
if (IsOpen == false)
{
SMSPort.Open();
ReadThread.Start();
}
}
public void Close()
{
if (IsOpen == true)
{
SMSPort.Close();
}
}
}
Then use the code as below:
SMSEngine = new SMSCOMMS("COM1");
SMSEngine.Open();
SMSEngine.SendSMS("919888888888","THIS IS YOUR MESSAGE");
SMSEngine.Close();
Sending SMS via a webservice
Sending SMS via webservices, although not for real-time services, is a very cost-effective solution. There are lots of webservices and you should be able to find one by searching the web. There are free ones that are not so reliable. So, purchase SMS credits to send a limited number of SMS using a webservice. Here, the usage is very simple, as it is just consuming a webservice to send a number and message to a function. The Code Project sample is available at The Code Project.
Sending SMS via service provider endpoints
Sending SMS via service provider is also similar to using a webservice. Here, it may be a non-standard protocol or over HTTP. It differs from service provider to service provider. Some provide sample code that can be used for programming custom applications.
History
- 1 June, 2007 -- Original version posted.
- 11 June, 2007 -- Article edited and posted to the main CodeProject.com article base.
