I mainly find notifications on my mobile phone annoying and have disabled most of them. But things are different when something requires my attention at home. The classic example is the doorbell: I want to know when a delivery person is standing at my front door even if I'm flooding my noise-killing headset with electric guitar music. I already solved this problem back in 2016 with a Raspberry Pi and described the setup in this column [1].

With my earlier solution, notifications reached me as Twitter direct messages, mainly because I didn't want to install a notification app just for this purpose. Twitter is already installed on my phone and provides a useful programming interface. However, Twitter is increasingly setting up hurdles for access to the API. For example, you now need to describe in a small, free text essay the purpose of your proposed use of the API. This may be understandable from the supplier's point of view, but I would prefer things to be a little simpler.

This explains why I now use the Telegram API [2]. Among other things, I can create bots that can be used to do many funny things. On top of this, I can get the bot to send me messages. You can create a bot by starting a chat with BotFather in the Telegram app (Figure 1).

Figure 1: Create a new bot by opening a conversation with the BotFather.

Start with the /newbot command. BotFather asks you for a name and a username for your bot. In return, you are sent a numeric ID and an access token – that is, a string that you have to pass to the API to identify yourself. It could look like this, for example:

919445171: AAFt4RTVEcI919fAI_5YGHX0A8QyQnY_fBA

The first few digits are your bot's numeric ID, followed by a colon and the access token. Now you have to start a chat with your bot in the app or the web interface [3]. This chat also has a numeric ID, which you need to discover. The curl command from Listing 1 does the trick.

$ curl -X POST https://api.telegram.org/bot919445171:AAFt4RTVEcI919fAI_5YGHX0A8QyQnY_fBA/getUpdates

Note that you need to prefix your bot's numeric ID with the bot keyword. For the most part, the long answer is unimportant for the purposes of this article, but it does contain a string reading "id":930313820 – this is the chat ID. Now you have all the information you need.

If you now want to automatically send a message to the bot chat, using a Bash script for example, the curl call from Listing 2 is all it takes. The phone vibrates and a message appears on the display (Figure 2). Now, I'll never miss my deliveries again.

$ curl -X POST 'https://api.telegram.org/bot919445171:AAFt4RTVEcI919fAI_5YGHX0A8QyQnY_fBA/sendMessage?chat_id=930313820&text="Hello world!"'

Figure 2: When the delivery person rings the bell, the bot is triggered and my phone vibrates.