MQTT Downlink issue


the downlink doesnt recieve by device, but on portal

recieves well,

what should be mistake?

I’m not 100% sure what you mean with this. By showing a screenshot of an empty queue, you mean it was sent by ChirpStack but not received by the device?

Thanks for rapid reach,

i want to downlink in 2 ways with MQTT,

Unicast ( single device)
and Multicast

need to make MQTT with C# application

here is my code sample but somethings wrong, can you assist me to fix it?

using MQTTnet;
using MQTTnet.Client;
using MQTTnet.Client.Options;
using System.Text;
using System.Threading.Tasks;

public class Program
    public static async Task Main(string[] args)
        // MQTT client oluştur
        var factory = new MqttFactory();
        var mqttClient = factory.CreateMqttClient();

        // MQTT client ayarları
        var options = new MqttClientOptionsBuilder()
            .WithTcpServer("YourMqttBrokerAddress", 1883) // Port numarası genellikle 1883'tür
            .WithCredentials("YourUsername", "YourPassword")

        // MQTT client'ı bağla
        await mqttClient.ConnectAsync(options);

        // Downlink mesajını oluştur
        var downlinkMessage = new
            confirmed = true, // Onaylanmış downlink mesajı mı?
            fPort = 1, // FPort değeri
            data = "SGVsbG8gd29ybGQ=" // Base64 formatında veri ("Hello world" örneği)

        // Downlink mesajını JSON'a çevir
        var downlinkMessageJson = JsonConvert.SerializeObject(downlinkMessage);

        // Downlink mesajını MQTT mesajına çevir
        var message = new MqttApplicationMessageBuilder()
            .WithTopic("application/{APPLICATION_ID}/device/{DEV_EUI}/command/down") // Uygulama ID'si ve cihaz EUI'si ile konuyu değiştirin

        // Downlink mesajını gönder
        await mqttClient.PublishAsync(message);


That’s totally true, i send from also hex data, its totally works fine but with mqtt application, it not got recieve from device, maybe i am missing some querry or url?

i didnt use deveui at payload json, problem may acquire becaause of that?