Telegram is a very versatile instant messaging software that can be used with the same phone number on different devices simultaneously.
In this tutorial we saw how to install it, and we tried to send text and media messages.
We have also seen that it is possible to set the Raspberry to send messages automatically.
In this tutorial we will ask Raspberry to take a specific action as a function of the received message, for example, we could send a text message with the word "photo" and Raspberry will sends us a photo of the apartment, or "lamp" to turn a lamp, or "open" to open the garage door.
Well, let's start

You need:

a Raspberry Pi B or B+, with the latest version of Raspbian, or our MIcroSD Card 8GB Class 10 Raspbian preinstalled.

Installation:

Read this tutorial, we use this configuration as start point.

To intercept a new incoming message we create a file action.lua

"Lua is a powerful, fast, lightweight, embeddable scripting language.

Lua combines simple procedural syntax with powerful data description constructs based on associative arrays and extensible semantics. Lua is dynamically typed, runs by interpreting bytecode for a register-based virtual machine, and has automatic memory management with incremental garbage collection, making it ideal for configuration, scripting, and rapid prototyping." From http://www.lua.org.

sudo nano /home/pi/tg/action.lua

with this content

function on_msg_receive (msg)
    if msg.out then
        return
    end
    if (msg.text=='ping') then
       send_msg (msg.from.print_name, 'pong', ok_cb, false)
    end
end
 
function on_our_id (id)
end
 
function on_secret_chat_created (peer)
end
 
function on_user_update (user)
end
 
function on_chat_update (user)
end
 
function on_get_difference_end ()
end
 
function on_binlog_replay_end ()
end

Save and exit, when incoming text message is "ping", Telegram answers us with a text message containing "pong".

move in tg

cd /home/pi/tg

then type

bin/telegram-cli -k tg-server.pub -W -s action.lua

Try to send a message, if all goes well, Telegram answers only on "ping" and not "PING", we should see something like this

Ok, let's do something more interesting.

Install the Raspberry Camera, see this tutorial, then create a new folder where we will save the captured photos.

sudo mkdir /home/pi/camera

create a new file camera.sh

sudo nano /home/pi/camera/camera.sh

with this content

#!/bin/bash  
 
raspistill -w 800 -h 600 -o /home/pi/camera/photo.jpg 
 

save and exit, give it execution permissions

sudo chmod -R 0655 /home/pi/camera/camera.sh

Edit action.lua

sudo nano /home/pi/tg/action.lua

add this lines in function on_msg_receive

if (msg.text=='photo') then
   os.execute('/home/pi/camera/camera.sh')
   send_photo (msg.from.print_name, '/home/pi/camera/photo.jpg', ok_cb, false)
end

Test it

bin/telegram-cli -k tg-server.pub -W -s action.lua

Now if you send a text message with "photo", Raspberry answer with a photo

To enter additional commands simply change the file action.lua inserting a new if block , for example, we could activate a relay or ask the status of a sensor.

In the next tutorials will achieve some other example of use.

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