Phoenix Channels Essentials

RULES

1. Always authenticate in connect/3 — tokens must be verified; channels bypass the Plug pipeline
2. Authorize in join/3 — verify the user can access the requested topic
3. Use handle_in for client-to-server, push for server-to-client, broadcast for server-to-all
4. Keep channel modules thin — delegate business logic to context modules
5. Use Presence for tracking connected users — don't roll your own presence tracking
6. Return {:reply, :ok, socket} or {:reply, {:error, reason}, socket} from handle_in — never silently drop messages

Setup Checklist