app.py

from slackeventsapi import SlackEventAdapter
import os

# Our app's Slack Event Adapter for receiving actions via the Events API
slack_signing_secret = os.environ["SLACK_SIGNING_SECRET"]
slack_events_adapter = SlackEventAdapter(slack_signing_secret, "/slack/events")

# Create a SlackClient for your bot to use for Web API requests
slack_bot_token = os.environ["SLACK_BOT_TOKEN"]
slack_client = SlackClient(slack_bot_token)

# Example responder to greetings
@slack_events_adapter.on("message")
def handle_message(event_data):
    message = event_data["event"]
    
    # Prints latest message to console
    print(message.get('text'))

# Error events
@slack_events_adapter.on("error")
def error_handler(err):
    print("ERROR: " + str(err))

# Once we have our event listeners configured, we can start the
# Flask server with the default `/events` endpoint on port 3000
slack_events_adapter.start(port=3000, host='0.0.0.0')