In this article I give you an example on how you can send SMS messages to
wireless devices from C#.Net. I assume, that you are familiar with Visual
Studio 2017 or 2019 and the basics of databases and the SQL language.
The solution described here can be used with a GSM Modem attached to your
PC for sending SMS messages or it can be used with IP SMS connections.
System architecture
The system architecture used for SMS messaging consists of a GSM Modem,
that is attached to the PC with a phone-to-PC datacable, an SQL-SMS Gateway
software installed onto your PC, an SQL database server, such as SQL Express
or MS SQL and your SMS application (Figure 1). As you can see on the figure,
your SMS application will create an SQL record in the database. The SMS
gateway will poll this record using
an SQL SELECT statement and will send it using a GSM modem.
Figure 1. - In house SMS messaging / system architecture
Preparing your database server
To get this architecture running, first you should prepare your database.
This means that you should create two database tables. One will be used
for sending SMS messages (ozekimessageout) and the other
will be used for receiving SMS messages (ozekimessagein). The database
table you create should contain a field for sender number, recipient
number and message text. For sending messages you also need a status
field, that will indicate whether the message has been sent.
The recommended database table layout can be seen on Figure 2. Please
note that you can add extra columns to this layout freely. After creating
the database table layout you should also create a username and a
password that can be used to log into database.
create database ozeki
GO
use database ozeki
GO
CREATE TABLE ozekimessagein (
id int IDENTITY (1,1),
sender varchar(30),
receiver varchar(30),
msg varchar(160),
senttime varchar(100),
receivedtime varchar(100),
operator varchar(30),
msgtype varchar(30),
reference varchar(30),
);
CREATE TABLE ozekimessageout (
id int IDENTITY (1,1),
sender varchar(30),
receiver varchar(30),
msg varchar(160),
senttime varchar(100),
receivedtime varchar(100),
operator varchar(100),
msgtype varchar(30),
reference varchar(30),
status varchar(30),
errormsg varchar(250)
);
GO
sp_addLogin 'ozekiuser', 'ozekipass'
GO
sp_addsrvrolemember 'ozekiuser', 'sysadmin'
GO
Figure 2. - Database table layout
Configuring the SMS Gateway
Once the database has been setup you should install and configure the
SMS Gateway. The SMS Gateway we use in this article is the Ozeki NG - SMS
Gateway it can be downloaded from www.ozekisms.com. There are
other similar SMS gateways available. We chose this SMS Gateway, because
it is very reliable, easy to configure and it is based on .NET which means
it integrates well into our architecture. In the SMS gateway
first you should configure the GSM modem attached to your PC. This can be
done by adding a GSM Modem service provider connection. Detailed steps:
Step 1.) Open http://127.0.0.1:9501 in Internet Explorer, login with
admin/abc123
Step 2.) In the "Serviceprovider connections" menu click on "Add service provider
connection", then select "GSM Modem Connection" and click "Install"
Step 3.) On the GSM modem configuration form, select the com port (usually COM1)
and click on autodetect to configure your modem
Step 4.) In the "Users and applications" menu click on "Add user", the select
"Database user" and click on "install"
Step 5.) For username provide "sql1"
Step 6.) For connection string type select "OleDb" and for connection string
enter:
Step 7.) In the configuration form I suggest you to turn on SQL logging.
You can do this by enabling the checkboxes:
"Log SQL SELECT statements" and "Log SQL UPDATE statements"
Figure 3. - SMS Gateway configured
After these steps you have configured the SMS Gateway to forward your messages
from the database to the mobile devices.
Creating your SMS application
Once the database has been prepared and the SMS Gateway has been setup you
can use Visual Studio.NET to create your SMS application. In Visual Studio
create a new project of "Windows Application" type (Figure 4). This
application will provide a GUI for sending the SMS message. It will connect
to the database server and will insert a new record when an message is
sent to a mobile phone.
Figure 4. - Application type: Windows Application
In this application you should have a form, that can be used by the user
of your app to compose the message (Figure 5). This form should contain a
field for the recipient number and another field for the message text. The
form will have a button, that will initiate the sending process.
Figure 5. - SMS Message form
To be able to connect to your database server you should include the "using
System.Data.OleDb;" directive in the using section for your code. The code
for sending the SMS message is written into the event handler
of the button. In this code first we connect to the database using an
OleDbConnection object. For the connection we use a standard connection
string. If the connection is successful (the state equals ConnectionState.Open),
we execute our SQL INSERT statement to insert the SMS message. To achieve
this we compose the SQL statement and we use an OleDbCommand object to execute
it (Figure 6).
private void button1_Click(object sender, EventArgs e)
{
try
{
//Connect to the database
OleDbConnection conn = new OleDbConnection();
conn.ConnectionString = "Provider=SQLNCLI;Server=.\\;"+
"User ID=ozekiuser;password=ozekipass;Database=ozeki;Persist
Security Info=True";
conn.Open();
if (conn.State == ConnectionState.Open)
{
//Send the message
OleDbCommand cmd = new OleDbCommand();
cmd.Connection = conn;
string SQLInsert =
"INSERT INTO "+
"ozekimessageout (receiver,msg,status) "+
"VALUES "+
"('"+tbSender.Text+"','"+tbMsg.Text+"','send')";
cmd.CommandText = SQLInsert;
cmd.ExecuteNonQuery();
MessageBox.Show("Message sent");
}
//Disconnect from the database
conn.Close();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
Figure 6. - Sending an SMS message source code
Verifying your SMS application
After executing the application, you can send your first SMS message. To
track the message you can use an SQL console to see what is inserted into
your SQL table and you should examine the event log of the SMS gateway
to see the SQL events. The eventlog of the Ozeki NG SMS gateway is located
at the following location:
