Program.cs

using MQTTnet.Client;
using MQTTnet.Extensions.ManagedClient;
using MQTTnet;
using System.Text.Json;

IManagedMqttClient _mqttClient = new MqttFactory().CreateManagedMqttClient();

// Create client options object
MqttClientOptionsBuilder builder = new MqttClientOptionsBuilder()
                                        .WithClientId("behroozbc")
                                        .WithTcpServer("localhost");
ManagedMqttClientOptions options = new ManagedMqttClientOptionsBuilder()
                        .WithAutoReconnectDelay(TimeSpan.FromSeconds(60))
                        .WithClientOptions(builder.Build())
                        .Build();



// Set up handlers
_mqttClient.ConnectedAsync += _mqttClient_ConnectedAsync;


_mqttClient.DisconnectedAsync += _mqttClient_DisconnectedAsync;


_mqttClient.ConnectingFailedAsync += _mqttClient_ConnectingFailedAsync;


// Connect to broker
await _mqttClient.StartAsync(options);

// Send a new message to the broker every second
while (true)
{
    string json = JsonSerializer.Serialize(new { message = "Hi Mqtt", sent = DateTime.UtcNow });
    await _mqttClient.EnqueueAsync("behroozbc.ir/topic/json", json);

    await Task.Delay(TimeSpan.FromSeconds(1));
}
Task _mqttClient_ConnectedAsync(MqttClientConnectedEventArgs arg)
{
    Console.WriteLine("Connected");
    return Task.CompletedTask;
};
Task _mqttClient_DisconnectedAsync(MqttClientDisconnectedEventArgs arg)
{
    Console.WriteLine("Disconnected");
    return Task.CompletedTask;
};
Task _mqttClient_ConnectingFailedAsync(ConnectingFailedEventArgs arg)
{
    Console.WriteLine("Connection failed check network or broker!");
    return Task.CompletedTask;
}