How to schedule an SMS in Visual Basic

The most simple way to send SMS from Visual Basic is to use the built in HTTP/Rest SMS api of Ozeki SMS Gateway. When you use this API, you will send SMS messages by issuing a HTTP Post request to the SMS gateway. The HTTP Post request will contain a message formatted in json format. The SMS gateway will send this SMS to the recipient phone, and it will return a HTTP 200 OK response to your request.

schedule sms for future delivery in visual basic
Figure 1 - Visual Basic schedule SMS for future delivery

Visual Basic code to send scheduled sms to mobile

The Visual Basic sms code sample below demonstrates how you can send SMS using the http rest sms api of Ozeki SMS Gateawy using the Visual Basic Ozeki.Libs.Rest library. This library is provided to you free of charge, and you may use it and modify it in any of your projects.

Imports Ozeki.Libs.Rest

Module Program
    Sub Main(args As String())

        Dim configuration As New Configuration
        configuration.Username = "http_user"
        configuration.Password = "qwe123"
        configuration.ApiUrl = ""

        Dim msg As New Message
        msg.ToAddress = "+36201111111"
        msg.Text = "Hello, World!"
        msg.TimeToSend = DateTime.Parse("2021-06-11 14:46:00")

        Dim api = New MessageApi(configuration)

        Dim result = api.Send(msg)


    End Sub
End Module

How to use the Visual Basic sms example:

This Visual Basic sms example can be used in any .NET or .NET core application. To use it, you must add the Ozeki.Libs.Rest dll as a reference to your project. After the project reference is added, you must put the using Ozeki.Libs.Rest; directive into the header section of your Visual Basic source code. This will allow you to use the classes provided by the Ozeki.Libs.Rest library. You can use the Message class to create the SMS. You can use the MessageApi class to send the SMS to the SMS gateway. The SMS gateway will forward your message to the mobile network either through a wireless connection or through the Internet.

Download SendScheduledSms.vb

The source code explained in this article can be downloaded and used and modified free of charge.
Download: (47.6Kb)

What is in the SendScheduledSms.vs file?

The SendScheduledSms.cs file contains the Ozeki.Libs.Rest library, which gives you all the tools neccessary to send and receive SMS messages. You will also find the SendScheduleSms project in the zip, which contains the example code to show you how to send an SMS. This example code is listed below.

Figure 2 - What is inside

How to send SMS from Visual Basic (Quick steps)

To send sms from Visual Basic:

  1. Install Ozeki SMS Gateway
  2. Connect Ozeki SMS Gateway to the mobile network
  3. Send a test sms from Ozeki GUI
  4. Create a HTTP sms api user
  5. Start Visual Studio
  6. Create a solution called SendScheduledSms.sln
  7. Add a Visual Basic console project: SendScheduledSms.vbproj
  8. Put the code into Program.vb or SendScheduledSms.vb
  9. Create a Visual Basic function called Send_SMS
  10. Create the SMS Json data
  11. Create a http request to send the SMS
  12. Read the HTTP response
  13. Write the response on the console
  14. Check the logs in the SMS gateway

Install Ozeki SMS Gateway and create an HTTP API user

To be able to send SMS from Visual Basic, first you need to install Ozeki SMS Gateway. The SMS gateway can be installed on the same computer, where you develop your Visual Basic code in Visual studio. After installation, the next step is to connect Ozeki SMS Gateway to the mobile network. You can send a test sms from the Ozeki GUI to verify, that your mobile network connection works. The final step to prepare your environment is to create a HTTP sms api user. Create a user with a username of "http_user", and with a password of "qwe123" to make the example work without modification.

After the environment is setup, you can run your Visual Basic code.

HTTP API url to use send sms from Visual Basic

To send SMS from Visual Basic, your Visual Basic will will have to issue an HTTP request to the SMS gateway. The API url is shown below. Note that the IP address ( should be replaced to the IP address of your SMS gateway. If Ozeki SMS Gateway is installed on the same computer where the Visual Basic sms application is running, this can be If it is installed on a different computer it should be the IP address of that computer.

HTTP authentication to use send sms from Visual Basic

To authenticate the Visual Basic sms client, you need to send the username and password in a base64 encoded string to the server in a HTTP request. The format used is: base64(username+":"+password). In C# you can use the following code to do this encoding:

var encoding = Encoding.GetEncoding("iso-8859-1");
var usernamePassword = username + ":" + password;
var usernamePasswordEncoded = Convert.ToBase64String(encoding.GetBytes(usernamePassword));

For example if you encode the username 'http_user' and the password 'qwe123', you will get the following base64 encoded string: aHR0cF91c2VyOnF3ZTEyMw==. To send

HTTP request header to send SMS from F#

To send the SMS messages, you need to include the following lines as headers in the HTTP request. Note that we include a content type and an Authorization header.

Content-Type: application/json
Authorization: Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==

HTTP request to send scheduled SMS from Visual Basic

To submit the SMS, your Visual Basic application will send an HTTP request similar to the one below. Note, that this requst contains a HTTP header part and a http body part. The HTTP body is a JSON encoded data string. It contains the recipient number and the messages text.

POST /api?action=sendmsg HTTP/1.1
Connection: Keep-Alive
Content-Length: 336
Content-Type: application/json
Authorization: Basic aHR0cF91c2VyOnF3ZTEyMw==

  "messages": [
      "message_id": "9f79a6bd-5264-4ebe-a04c-4f1353c54657",
      "to_address": "+36201111111",
      "text": "Hello, World!",
      "create_date": "2021-06-11 14:34:41",
      "valid_until": "2021-06-18 14:34:41",
      "time_to_send": "2021-06-11 14:46:00",
      "submit_report_requested": true,
      "delivery_report_requested": true,
      "view_report_requested": true,
      "tags": []

HTTP response received by the Visual Basic sms example

Once the SMS gateway receives this request, it will generate a HTTP response. The HTTP response will contain a status code, to indicate whether the SMS submit request was successful or not. It will also return a JSON encoded structure to provide you useful details about the messages submission.

HTTP/1.1 200 OK
User-Agent: OZEKI 10.3.118 (
Content-Type: application/json; charset=utf8
Last-Modified: Fri, 11 Jun 2021 08:44:45 GMT
Server: 10/10.3.118
Transfer-Encoding: chunked

  "http_code": 200,
  "response_code": "SUCCESS",
  "response_msg": "Messages queued for delivery.",
  "data": {
    "total_count": 1,
    "success_count": 1,
    "failed_count": 0,
    "messages": [
        "message_id": "ca824cbe-784c-44f9-b657-1c04f711f529",
        "from_station": "%",
        "to_address": "+36201111111",
        "to_station": "%",
        "text": "Hello, World!",
        "create_date": "2021-06-11 14:34:41",
        "valid_until": "2021-06-18 14:34:41",
        "time_to_send": "2021-06-11 14:46:00",
        "submit_report_requested": true,
        "delivery_report_requested": true,
        "view_report_requested": false,
        "tags": [
            "name": "Type",
            "value": "SMS:TEXT"
        "status": "SUCCESS"

Visual Basic sms example: SendScheduledSms.sln

How to download the example project (Video tutorial)

In this video, you will learn how to download and run the SendScheduledSms.sln example project. The video will start with the download page and will end with the opened code editor. You will learn how to download and how to open the Visual Basic example code. This very detailed video is only 1 minute long and easy to understand. Don’t worry you will have no problem following it.

Video 1 - How to download and run the example project above

The example code below is part of the SendScheduledSms.sln Visual Studio Solution. A visual studio solution can contain multiple projects and multiple files. In this solution there is only one project: SendScheduledSms.vbproj, and one file: Program.vb.

how to send scheduled sms with visual basic
Figure 3 - SendScheduledSms.sln

How to use the example porject

In the next video, you will learn how to run the example code and how to check the log of the process. It will start with launching the Ozeki SMS Gateway and will take you all the way to the list of postponed messages. You will learn how to check the log and how to launch the project to send the scheduled messages. The video in only 1:22 minute long so you will have no problem understanding it. We use the Ozeki SMS Gateway software for logging and SMS sending. It is a powerful yet easy to learn gateway software.

Video 2 - How to use the SendScheduledSms.vb solution

Runing the Visual Basic sms example on Windows

When you use windows to run this sms example written in Visual Basic, you will notice that you get slightly better performance, than when you run it on Linux. To understand why this happens, you must bring into mind that Visual Basic is using the .NET framework for code execution. This is because the .NET implementation on Windows is optimized for performance, while mono, the .NET implementation on Linux has some catching up to do in this field.


The purpose of this article was to show the steps of SMS scheduling in VB with the help of Ozeki SMS Gateway. The tools and explanation are provided by Ozeki. If you read everything carefully and done all steps, you should be able to schedule the messages in Visual Basic.

Ozeki SMS Gateway can be downloaded from Ozeki's website and can be used in a trial period, which is completely free. Scheduling messages allows you to send SMS to mobile users when they are not busy, meaning that you can work with higher efficiency.

Make sure to not finish your reading here, check out Ozeki's tutorial page where there is more information about similar topics, like SMS deleting and receiving in VB.

Your next thing to do is to download Ozeki SMS Gateway and let the work begin!

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