Become aware of your app events in Telegram

Sure you have used multiple services that allows you send app notifications, like Pushover or even IFTTT, but in this case, we are going to use Telegram to send notifications about what is happening in your application.

In Telegram, we cannot just send direct notifications to users. So first and foremost we will need to sign up for a bot, which will be responsible of send on our behalf all the notifications we would like to send. To this end, Telegram has another bot called @botFather (official Telegram bot), which we can use to create a new bot for us.

Once the name and username have been set, we will be provided with an API key to be used to make authenticated requests for our new bot.

Setting up our webhook

For our example, we will set up our bot to work using webhook calls to our endpoint. In order to do this, we have an API method called setWebook.

We will configure our URL, where we will be waiting for requests, in example: http://testbot.test.com/webhook. Also we will register only for new messages, using the allowed_updates parameters:

const apiKey = '1339494003:AAHxiTIXM-oarKGVIufH3A_iaLZT7gWrDRg';
const url = `https://api.telegram.org/bot${apikey}/setWebhook`;
const webhookUrl = 'http://testbot.test.com/webhook';

const result = await fetch(url, {
    method: 'POST',
    body: JSON.stringify({
        url: webhookUrl,
        allowed_updates: ['message']
    }),
    headers: {
        'content-type': 'application/json'
    }
});

Once completed, any message received by our bot, will be forwared to our webhook.

You might wonder, why should I configure an endpoint to receive messages if I just want to send them? This is required in order to get the chat identifier, which relates a user with our bot. Thanks to this identifier we will be able to send messages to the user

Getting the chat identifier

First of all, we will need to create a new controller for the previously defined webhook. To begin with, making a console.log and logging the body of the request, will be enough. After this, we will send a message to our bot (For instance, the suggested /start command).

We will not get any answer, but Telegram will be responsible for calling our webhook with a body like this one:

{
   "update_id":9079187,
   "message":{
      "message_id":1,
      "from":{
         "id":283433899,
         "is_bot":false,
         "first_name":"Gilber",
         "username":"jgmullor",
         "language_code":"en"
      },
      "chat":{
         "id":283433899,
         "first_name":"Gilber",
         "username":"jgmullor",
         "type":"private"
      },
      "date":1601201881,
      "text":"/start",
      "entities":[]
   }
}

With this request, we got the identifier we were looking for, and the one with we can start sending notifications from our application events.

The first message

Therewith, we are ready to send messages, so we will be using the sendMessage API method, like in this example:

const apiKey = '1339494003:AAHxiTIXM-oarKGVIufH3A_iaLZT7gWrDRg';
const url = `https://api.telegram.org/bot${apiKey}/sendMessage`;
const text = 'This is a test'
const chatId = '283433899';

const result = await fetch(url, {
    method: 'POST',
    body: JSON.stringify({
        chat_id: chatId,
        text: text,
        parse_mode: 'HTML'
    },
    headers: {
        'content-type': 'application/json'
    }
});

After this request…

We have finally received a message from our bot!

Hereon…

Now we are ready to send messages from our application, like critical events that require a prompt notice. But this is not the end, we can keep extending this into:

• Receiving messages: Configure your application based on received messages, or make requests without opening any browser or app, only sending a message to your bot (Example: Set order 93928 as sent using a command like /sent 93928)
• Order status: Allow your users to get updates about their orders, you can ask your users to send your bot a command like: /status 93928 my@email.com in order to get their order status.

Quite literally, the options are endless 🙂

Moreover, remember that you have all the code in an example application in this Github repository.