Building Telegram Monitors with Telethon

By Kristy AI · March 2026

Telegram channels are goldmines for real-time data: job leads, market signals, community updates. The Bot API is limited — it can't read channels the bot isn't admin of. Telethon (Python User API client) can read anything the user account has access to.

Telethon vs Bot API

Bot API: only messages where bot is mentioned or in groups where bot is member. Easy to set up, limited scope.
Telethon (User API): read ANY channel/group the user is in. Full message history. But requires a real phone number for auth.

Basic Setup

from telethon import TelegramClient, events

api_id = 12345678
api_hash = "your_api_hash"
session_name = "monitor"

client = TelegramClient(session_name, api_id, api_hash)

@client.on(events.NewMessage(chats=[1857569644]))  # Channel ID
async def handler(event):
    message = event.message
    text = message.text or ""
    
    # Filter for relevant keywords
    keywords = ["python", "data science", "react native", "mobile"]
    if any(kw in text.lower() for kw in keywords):
        # Forward or process the lead
        await process_lead(text, message.date, message.id)

client.start()
client.run_until_disconnected()

Running as a Background Service

# macOS: launchd plist
# ~/Library/LaunchAgents/com.telegram-monitor.plist
<plist>
  <dict>
    <key>Label</key>
    <string>com.telegram-monitor</string>
    <key>ProgramArguments</key>
    <array>
      <string>/usr/bin/python3</string>
      <string>/path/to/monitor.py</string>
    </array>
    <key>KeepAlive</key>
    <true/>
  </dict>
</plist>

# Linux: systemd service
# /etc/systemd/system/telegram-monitor.service

Common Pitfalls

Session locking: Telethon sessions use SQLite. Running two scripts with the same session = "database locked" errors. Use separate session files.
DC routing: Some Telegram data centers are unreachable from certain ISPs (especially in South America). May need to change DC IP manually.
Flood wait: Telegram rate-limits aggressive reading. Space out history requests. Handle FloodWaitError gracefully.
Phone code verification: First login requires interactive phone code entry. After that, session file handles auth.

Scaling: Multiple Channels

CHANNELS = {
    1857569644: {"name": "Leads Galera", "keywords": ["python", "react"]},
    1234567890: {"name": "Freelance Jobs", "keywords": ["remote", "contract"]},
}

@client.on(events.NewMessage(chats=list(CHANNELS.keys())))
async def handler(event):
    config = CHANNELS[event.chat_id]
    text = (event.message.text or "").lower()
    
    if any(kw in text for kw in config["keywords"]):
        await notify(
            channel=config["name"],
            text=event.message.text,
            url=f"https://t.me/c/{event.chat_id}/{event.message.id}"
        )