Miscelaneous

Usually, you'll want to subscribe to a widcard topic like downlink/#.

Reboot Device

Reboot can be triggered using Device Menu -> Reboot.

You will get a message on downlink/reboot topic, with an empty payload.

mosquitto_sub -h blynk.cloud -p 8883 -u device -P '{DEVICE_TOKEN}' -t 'downlink/reboot'

Ping Device

This feature is activated using Device Menu -> Ping.

The server publishes downlink/ping topic, with QOS 1 and an empty payload. Subsequently, the client should automatically respond with an MQTT PUBACK packet, in accordance with the MQTT standard.

mosquitto_sub -h blynk.cloud -p 8883 -u device -P '{DEVICE_TOKEN}' -t 'downlink/ping'

Reconfigure Device

This feature is activated using a Device -> Info Icon -> Three dots -> Reconfigure button in the mobile application (see the Mobile App Device Actions menu section).

The server publishes the downlink/reconfigure topic with an empty payload. Subsequently, the device should enter the Wi-Fi configuration stage, by broadcasting a Wi-Fi Access Point and asking the user to enter the new Wi-Fi network credentials.

mosquitto_sub -h blynk.cloud -p 8883 -u device -P '{DEVICE_TOKEN}' -t 'downlink/reconfigure'

Last Will and Testament

Upon connection, the client can specifiy the Last Will message along with the topic to which it should be published. If the client loses connection without sending a proper MQTT DISCONNECT message, the broker will publish this pre-determined Last Will message.

Server Diagnostics

The server has the capability to publish messages under the downlink/diag topic under certain circumstances, typically when it detects potentially problematic behavior from the client. These diagnostic messages are designed to be observed and addressed by developers.

mosquitto_sub -h blynk.cloud -p 8883 -u device -P '{DEVICE_TOKEN}' -t 'downlink/diag'