Configure The Things Stack MQTT integration for uplink and downlink messages

Steps

1. In the TTS console, navigate to Applications > your app > Integrations > MQTT and note the public MQTT endpoint hostname and port (1883 for plain TCP, 8883 for TLS).
2. Generate API key credentials with the appropriate rights (Read application traffic, Write downlink) from the API Keys section; use the application ID as the MQTT username and the API key as the password.
3. Subscribe to uplink messages using the topic v3/APP_ID@TENANT_ID/devices/+/up to receive all device uplinks as JSON, or narrow to a specific device by replacing + with DEVICE_ID.
4. To schedule a downlink, publish a JSON payload to v3/APP_ID@TENANT_ID/devices/DEVICE_ID/down/push; include the frm_payload as base64-encoded bytes, f_port, and optionally confirmed flag.
5. Parse the uplink JSON structure: decoded_payload contains the formatter output, uplink_message.rx_metadata includes gateway RSSI and SNR, and received_at is the server-side timestamp.
6. Use TLS on port 8883 and verify the server certificate against the TTS CA to prevent MQTT credential interception on untrusted networks.