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Simple Telegram Bot demo

Welcome to the tutorial explaining how to create a new bot for Telegram. In this article you will find:

• Create a new bot
• Generate self-signed certificate (optionsl)
• Set up simple Reverse Proxy using Nginx
• Register webHook in Telegram
• Deploy your first bot and use it via messenger

Create Bot

To create your bot you should ask @BotFather to do it. Simply send a personal message /newbot to him and follow the instructions.

Generate self-signed certificate

If you have your domain with trusted certificates for it, please skip this chapter. If you wish to use LetsEncrypt, then you may take some ready solutions, like that image, but LetsEncrypt doesn't allow to generate certificates for bare IP address. That means if you have a domain for your service, go ahead and use LE. Otherwise, you have to generate self-signed certificate to set up a webhook to Telegram because this messenger requires mandatory https for the backend. Thus, performs the following actions:

1. Edit the san.cnf file

Sometimes, the Alternative Names could prevent validating the domain, so, open the san.cnf file and provide valid IP addresses instead of "1.2.3.4". This will add valid SAN section to your certificate

2. Generate certificate

Call this command

openssl req -newkey rsa:2048 -sha256 -nodes -keyout /path/to/nginx/key.pem -x509 -days 365 -outform pem  -out /path/to/nginx/cert.pem -subj "/C=UK/ST=London/L=London/O=Daxi Digital/CN=1.2.3.4" -config /path/to/nginx/san.cnf

where:

• -keyout /path/to/nginx/key.pem is the path where the private key will be saved
• -days 365 the time for validity, one year in this example
• -outform pem we expect PEM format for our certificate
• -subj "/C=UK/ST=London/L=London/O=Daxi Digital/CN=1.2.3.4" don't forget to provide valid IP address
• -config /path/to/nginx/san.cnf use san.cnf file that we edited on the previous step

As result you will get two files: key.pem and cert.pem

3. Generate Diffie Hellman Ephemeral Parameters

run this command from the nginx directory:

openssl dhparam -out dhparam.pem 4096

this will take a while.

Set up Reverse Proxy using Nginx

Ok, now you are ready to set up the Nginx as a reverse proxy. Before you begin, take a look at the default.conf file. It redirects all the traffic to the http://172.17.0.1:8444, which is the inner IP address of Docker Gatweay. If you run your bot without a container, then let this line without modification. If you want to run it with docker-compose, then change the IP address to proper host.

Then build the Docker with Nginx:

sudo docker build -t bot-nginx .

and start it:

sudo docker run -d --name bot-nginx -p 8443:8443 bot-nginx

Cool! Now you have a nice Reverse Proxy that redirects all the traffic to the localhost:8444 and manages certificates that you generated in step 2.

Register WebHook

It's time to tell Telegram, that you have a ready backend for your bot. Simply call (don't forget to change IP address to yours and provide your bot API key):

curl -F "url=https://1.2.3.4:8443/<bot API Key>" -F "certificate=@/path/to/nginx/cert.pem" https://api.telegram.org/bot<bot API key>/setWebhook

if you want to debug the calls, you can use this call:

http https://api.telegram.org/bot<Bot Api Key>/getWebhookInfo

it will print to you the debug data about your webhook.

Deploy your first bot and use it via messenger

Generally, now you need simply to run your bot on the localhost. In my case I am using Go language, thus you need to compile it and then run. To compile, do:

go build

you will get demo-bot file. Copy this binary file to your server and on this server do:

./demo-bot

Have a fun!