C# MQTT通讯

前言

MQTTnet是Mqtt的net版本。国内MQTTnet教程比较老旧，都是2.x版本。MQTTnet在4.x版本版本代码逻辑有比较大的改动。所以最后还是面向Github编程。

EMQ X介绍及安装

长链接(MQTT)测试及工具MQTTX使用

MQTTnet

MQTTnet Github官网

MQTTnet简单案例

MQTTnet比较难，要熟练掌握Task异步方法的使用。

MQTT初始变量

//MqttClient工厂
 private MqttFactory mqttFactory = new MqttFactory();
 //MqttClient对象
 private IMqttClient mqttClient;
 //MqttClient连接选项
 private MqttClientOptions options;
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构造函数初始化

  mqttClient = mqttFactory.CreateMqttClient();
  options = new MqttClientOptionsBuilder()
  .WithTcpServer(IP地址, 端口号)
  .WithCredentials(用户名, 密码)
  .WithClientId(ClientId)
  .Build();
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连接Mqtt服务器

public async Task Connect()
{
    await mqttClient.ConnectAsync(options);
    if (mqttClient.IsConnected)
    {
        Console.WriteLine("连接成功！");
    }
    SubTopics.ForEach(async item =>
    {
        await mqttClient.SubscribeAsync(item);
        Console.WriteLine($"订阅:{item}");


    });
    HMACSHA256("fa34e04e-43b2-5309-817d-953e9576a07d", "2020050617");
    Console.WriteLine("服务器连接成功！");



}
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发送数据

        /// 

        /// 发送
        /// 
        public Task Send(string topic, object payload)
        {
            var msg = new MqttApplicationMessageBuilder()
            .WithTopic(topic)
            .WithPayload(JsonConvert.SerializeObject(payload))
            .Build();
            Console.WriteLine("发送信息");
            Console.WriteLine($"{topic}");

            Console.WriteLine($"{JsonConvert.SerializeObject(payload)}");
            return mqttClient.PublishAsync(msg);
        }
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添加订阅

//订阅事件
await mqttClient.SubscribeAsync(item);

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//订阅事件消息接收
mqttClient.ApplicationMessageReceivedAsync += e =>
            {
                Console.WriteLine("收到消息");
                Console.WriteLine($"Topic:{e.ApplicationMessage.Topic}");
                Console.WriteLine($"Message:{e.ApplicationMessage.ConvertPayloadToString()}");

                return Task.CompletedTask;
            };
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我们一般主要做的是客户端，详情请看MQTTnet 客户端Github示例