Mattermost intergrate with rasa. Connection refused

Hi everyone i have some issue when connect my rasa-chatbot to mattermost.
i follow the tutorial in rasa doc but the log display that connect: connection refused
i dont know about this error and how to handle that. Please help me.
This is my setting:

Why do you have the webhook_url part commented out? That could be causing the issue. This should be the url for wherever rasa is running, like http://localhost:5005/webhooks/mattermost/webhook for example