---
title: "Downlink using MQTT"
slug: "downlink-using-mqtt"
updated: 2024-08-30T06:42:17Z
published: 2024-08-30T06:42:17Z
canonical: "docs.connect.netmoregroup.com/downlink-using-mqtt"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://docs.connect.netmoregroup.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Downlink using MQTT

If connected to our [MQ Broker](/lora-portal/docs/mqtt-netmore), a downlink can be sent to a sensor using MQTT and response will be sent back over MQTT. If a request times out, the message will be dropped.

## Topics

The request should be sent to the topic “downlink” (just that, nothing more). The response will be received on a topic similar to the payload:

![](https://cdn.document360.io/58c1b868-b36b-492e-aea3-32180613f31f/Images/Documentation/Screenshot%202024-07-05%20082050.png)

## Format

Downlink Request

```json
{
	"devEui": "string (mandatory)",
	"payloadHex": "string (hex, mandatory)",
	"fPort": "string (integer, mandatory)",
	"requestId": "string (optional)",
    "validity": "string (seconds, ttl, mandatory on some LNS)",
}
```

if validity is set the downlink will be discarded after this number of seconds.

## Examples

**Downlink Request**

```json
{
	"devEui": "70B3D52A1FF00001",
	"payloadHex": "8303",
	"fPort": "1",
	"requestId": "MyRequestId-123",
    "validity": "300"
}
```

**Downlink Response 1a – queued for sending to the sensor**

```json
{
	"requestId": "MyRequestId-123",
	"deliveryStatus": "QUEUED",
	"devEui": "70B3D52A1FF00001"
}
```

**Downlink Response 1b – invalid request**

```json
{
	"requestId": "MyRequestId-123",
	"deliveryStatus": "ERROR_SENDING",
	"devEui": "70B3D52A1FF00001",
	"errorCode": "PAYLOAD_MISSING",
	"errorDescription": "Payload can't be empty"
}
```

**Downlink Response 2 – downlink is sent over the air**

```json
{
	"requestId": "MyRequestId-123",
	"deliveryStatus": "DOWNLINK_SENT",
	"devEui": "70B3D52A1FF00001"
}
```

## Types

**Delivery Statuses**

| **Code** |
| --- |
| QUEUED |
| ERROR_SENDING |
| DOWNLINK_SENT |

**Error Codes**

| Code | Explanation |
| --- | --- |
| FPORT_MISSING | FPort can't be empty |
| FPORT_INVALID | FPort must be an integer |
| PAYLOAD_MISSING | Payload can't be empty |
| SENSOR_NOT_PROVISIONED | Sensor not provisioned |
| VALIDITY_MISSING | Validity can't be empty for this LNS |
| VALIDITY_INVALID | Validity must be an integer |