Relaygram

Relaygram is a multilingual Telegram relay bot that forwards messages from one channel to another and saves attached files locally.

🧠 Purpose

This project automatically monitors a Telegram channel to:

• Download any attached files
• Forward all new messages (whether they contain files or not) to another channel

It is built with Python using the Telethon library and supports Docker deployment.

🌍 Language Support

The interface messages (CLI outputs) are multilingual and controlled via the LANG variable in your .env file.

• LANG=fr for French
• LANG=en for English

The default language is French if not specified.

🔐 Telegram Authentication

Before using the bot, you need to generate a persistent Telegram session.

Steps:

1. Go to https://my.telegram.org
2. Create an app to get your API_ID and API_HASH
3. On the first launch, the script will guide you to generate a StringSession:
   • Enter your phone number
   • Enter the code you receive by SMS or Telegram
   • Copy the generated session string
   • Paste it into the .env file under SESSION_STRING

This session will be reused automatically on each launch.

⚙️ Execution Modes

You can choose between two modes using the MODE variable in .env:

🧪 Development Mode (dev)

• Displays a terminal menu with a list of your channels
• You manually select the source channel to monitor
• The destination channel is defined in .env

🚀 Production Mode (prod)

• Both source and destination channels are set in .env
• No user interaction is needed
• Ideal for automated server deployment

📁 Project Structure

• generate_session.py : generates the StringSession
• main.py : main bot script
• start.py : entrypoint that checks for session and launches the right script
• lang.py : contains multilingual CLI messages
• downloads/ : where received files are saved
• .env : environment configuration (not versioned)
• .env.example : configuration template
• Dockerfile : defines the Docker image
• docker-compose.yml : simplifies containerized execution
• README.md : this documentation

⚙️ Environment Variables (.env)

Required variables:

• API_ID : your Telegram app ID
• API_HASH : your Telegram app hash
• SESSION_STRING : persistent session string
• MODE : either dev or prod
• SOURCE_CHANNEL_ID : source channel ID (used only in prod)
• TARGET_CHANNEL_ID : destination channel ID (used in both modes)
• LANG : fr or en (optional)

🐳 Useful Docker Commands

🔧 Build the Docker image

Run this only once, or after modifying the Dockerfile:

docker compose build

▶️ Interactive launch (dev mode)

Run the bot in development mode. You'll be able to choose the source channel manually:

docker compose run --rm relaygram

🚀 Automatic launch (prod mode)

Run the bot in production mode using .env configuration, with no user interaction:

docker compose up -d

📝 Final Notes

• Authentication happens only once: the Telegram session is saved.
• You must be a member of both source and destination channels.
• Only new messages are forwarded – history is not retrieved.