# Topic Structure ## Downlink These topics are used for messages sent from Blynk.Cloud to the device: * [**downlink/ds/`DATASTREAM`**](/en/blynk.cloud-mqtt-api/device-mqtt-api/datastreams.md): Carries live updates of datastream values or responses to get/ds requests. This ensures that the device is updated with the latest values or specific data it requested. * [**downlink/meta/`FIELD`**](/en/blynk.cloud-mqtt-api/device-mqtt-api/metadata.md): Used to receive a real-time metadata values update as well as to send responses for `get/meta` requests made by the device. This allows the device to update its configuration or status based on cloud-side settings or information. * [**downlink/ota/json**](/en/blynk.cloud-mqtt-api/device-mqtt-api/ota.md): Requests from the server to perform a software/firmware update. * [**downlink/utc/all/json**](/en/blynk.cloud-mqtt-api/device-mqtt-api/timezone-location.md): Device Time and Timezone information. Used to send response for `get/utc/all/json` request made by the device. * [**downlink/loc/all**](/en/blynk.cloud-mqtt-api/device-mqtt-api/timezone-location.md): Device approximate location. Used to send response for `get/loc/all` request made by the device. * [**downlink/ping**](/en/blynk.cloud-mqtt-api/device-mqtt-api/miscelaneous.md): Allows server to ping the device. This message is always published with `QOS 1`. * [**downlink/reconfigure**](/en/blynk.cloud-mqtt-api/device-mqtt-api/miscelaneous.md#reconfigure-device): Instructs the device to enter the Wi-Fi configuration stage. * [**downlink/reboot**](/en/blynk.cloud-mqtt-api/device-mqtt-api/miscelaneous.md): Instructs the device to reboot. This can be necessary for applying updates, resetting the device's state, or troubleshooting. * [**downlink/redirect**](/en/blynk.cloud-mqtt-api/device-mqtt-api/authentication.md#server-redirect): Provides a new MQTT endpoint to which the device should connect. This is part of handling GeoDNS and ensuring the device connects to the most suitable server for improved performance and reliability. * [**downlink/diag**](/en/blynk.cloud-mqtt-api/device-mqtt-api/miscelaneous.md): Server diagnostics messages. ## Uplink These topics are used for messages sent from the device to Blynk.Cloud: * [**info/mcu**](/en/blynk.cloud-mqtt-api/device-mqtt-api/authentication.md#firmware-and-device-info): Updates the server with device or firmware information. This is essential for device management and monitoring, allowing Blynk.Cloud to keep track of device types, versions, and other critical information. * [**ds/`DATASTREAM`**](/en/blynk.cloud-mqtt-api/device-mqtt-api/datastreams.md): Updates the value of a specific datastream on the cloud. This is how sensor readings, state changes, or any other device-generated information are communicated to the server. * [**batch\_ds**](/en/blynk.cloud-mqtt-api/device-mqtt-api/datastreams.md#send-batched-data-to-blynk): Updates values of a multiple datastreams simultaneously. Use this topic if your device rarely sends data in batches. * [**ds/`DATASTREAM`/prop/`PROPERTY`**](/en/blynk.cloud-mqtt-api/device-mqtt-api/widget-properties.md): Sets a property of the widget associated with a datastream, allowing dynamic changes to how data is displayed or interacted with in the Blynk application. * [**event/`EVENT`**](/en/blynk.cloud-mqtt-api/device-mqtt-api/events.md): Publishes an event, which can be used for alerts, emails, push notifications, logging, or triggering other server-side actions based on device activities. * [**meta/`FIELD`**](/en/blynk.cloud-mqtt-api/device-mqtt-api/metadata.md): Updates a specific metadata field of the device. This can include configuration parameters, or any other contextual information about the device. * [**get/ds**](/en/blynk.cloud-mqtt-api/device-mqtt-api/datastreams.md): Requests the current value of a specific datastream from Blynk.Cloud. This can be used to synchronize device state with server-side values. * [**get/meta**](/en/blynk.cloud-mqtt-api/device-mqtt-api/metadata.md): Requests metadata values from Blynk.Cloud, useful for devices needing to confirm or update their configuration based on cloud-stored information. * [**get/utc/all/json**](/en/blynk.cloud-mqtt-api/device-mqtt-api/timezone-location.md): Requests time-related information, assisting in time synchronization or scheduling tasks based on accurate time data. * [**get/loc/all**](/en/blynk.cloud-mqtt-api/device-mqtt-api/timezone-location.md): Requests approximate location information, which can be used for location-based services, astronomical timers or contextual actions based on the device's location. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.blynk.io/en/blynk.cloud-mqtt-api/device-mqtt-api/topic-structure.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.