使用 MQTTnet 匿名存取遠端 mosquitto Broker

前言

在前一篇 C# MQTT using MQTTnet 中，透過 ManagedMqttClient 可以接收到 mosquitto 的訊息。
可是，當我將 mosquitto 安裝在 Azure VM(20.121.35.xxx) 後，
啟動 mosquitto 服務後，從本機 Client 這卻連不到它。

解決

Firewall 設定

要在 Azure VM 中要允許 1833 Port 連入，

1.在 Network security group 設定 Inbound port rules ，
允許 TCP 1883 允許連入。

2.在 OS 控制台 Windows Defender Firewall 中的 Advanced settings 設定 Inbound Rules

設定 mosquitto 及測試

將 mosquitto 服務起動後，
可以在 Command 視窗中下 netstat -an | findstr 1883 來查看一下是否有針對 1883 Port 在 LISTENING，
內容如下，

從上圖可以發現，有針對 1883 Port 在 LISTENING，
但它只允許本機存取，因為是 127.0.0.1:1883，
必須為 0.0.0.0:1883 才會允許遠端存取。

1.調整 mosquitto.conf
新增 listener 1883，並先允許匿名存取

# listener port-number [ip address/host name/unix socket path]
listener 1883

# ...
allow_anonymous true

• 註:目前為測試不同機器存取，請勿設定在正式環境

重啟服務後，在 Command 視窗中下 netstat -an 就可以發現，
已變成 0.0.0.0:1883 。

2.修改 MQControlCenter 專案
原本 MQControlCenter 專案 Server 固定為 localhost ，
改成從 Command 視窗中讀取使用者的輸入值，
並執行起來，

using MQTTnet.Client;
using MQTTnet.Extensions.ManagedClient;
using MQTTnet;
using System.Text.Json;
using static System.Console;
using System.Text;
using MQTTnet.Packets;

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

var clientId = "controlCenter";

WriteLine("請輸入 MQTT Broker Server:");
var server = ReadLine();
if (string.IsNullOrWhiteSpace(server))
{
    server = "localhost";
}

var builder = new MqttClientOptionsBuilder()
                .WithClientId(clientId)
                .WithTcpServer(server);

var 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;
_mqttClient.ApplicationMessageReceivedAsync += _mqttClient_ApplicationMessageReceivedAsync;

var topicFilters = new List<MqttTopicFilter> { new MqttTopicFilter { Topic= "home/temperature/#" } };
await _mqttClient.SubscribeAsync(topicFilters);

WriteLine($"{clientId} 連線到 MQTT Broker ({server}) ....");
await _mqttClient.StartAsync(options);
WriteLine("Press any key to stop receive message ...");
ReadKey();

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

Task _mqttClient_ApplicationMessageReceivedAsync(MqttApplicationMessageReceivedEventArgs arg)
{
    var topic = arg?.ApplicationMessage?.Topic;
    var payloadText = Encoding.UTF8.GetString(
            arg?.ApplicationMessage?.Payload ?? Array.Empty<byte>());

    WriteLine($"Received: Topic:{topic}, Payload:{payloadText}");
    return Task.CompletedTask;
}

3.mosquitto_pub發佈訊息

mosquitto_pub -t "home/temperature/sensor1" -m "hello world"
mosquitto_pub -t "home/temperature/sensor2" -m "message from azure vm"
mosquitto_pub -t "home/temperature/sensor3" -m "message from azure vm sensor3"

4.最後在本機 Client 可以接收來自 Azure VM (MQTT Broker Server) 的訊息

參考資源

C# MQTT using MQTTnet