mqtt.js 客户端封装

mqtt.js 客户端封装

没封装前使用

const client = mqtt.connect('ws://broker.emqx.io:8083/mqtt')
onMounted(() => {
  const topicList = []
  const channelCount = 12
  for(let i = 0; i < channelCount; i++) {
    topicList.push(`/test/sendImage${i + 1}`)
  }

  client.on('connect', () => {
    console.log('connected')
    topicList.forEach((topic) => {
      client.subscribe(topic)
    })
    client.on('message', (topic, message) => {
      // 主要差别在这里，需要判断 topic 是当前订阅的，才进行处理，
      // 每次需要遍历所有的 topic 
      topicList.forEach((t, index) => {
        if(topic === t) {
          handleImage(message, index)
        }
      })
    })
  })
  client.on('error', (error) => {
    console.error('mqtt connect error', error)
  })
})
onUnmounted(() => {
  client.end()
})

封装后使用

const client = new Mqtt()
client.connect('ws://broker.emqx.io:8083/mqtt')

onMounted(() => {
  const topicList = []
  const channelCount = 12
  for(let i = 0; i < channelCount; i++) {
    topicList.push(`/test/sendImage${i + 1}`)
  }
  topicList.forEach((topic, index) => {
    // 订阅topic时，注册 callback，
    // 当前topic接收到的数据在 callback 中处理
    client.subscribe(topic, (message) => {
      handleImage(message, index)
    })
  })
})
onUnmounted(() => {
  client.disconnect()
})

封装 Mqtt class

原理是 subscribe 时，注册当前topic处理的 callback，在callback中处理接收到的数据

import mqtt, { IClientOptions, MqttClient } from 'mqtt';

export class Mqtt {
  private client: MqttClient | null = null;
  /**
   * 连接到 MQTT 服务器
   * @param brokerUrl
   * string: MQTT 服务器地址，
   * IClientOptions: 客户端配置
   * @param opts
   * @returns
   */
  connect(brokerUrl: string): MqttClient
  connect(opts: IClientOptions): MqttClient
  connect(brokerUrl: string, opts?: IClientOptions): MqttClient
  connect(
    brokerUrl: string | IClientOptions,
    opts?: IClientOptions,
  ): MqttClient {
    if(this.client) {
      console.warn('MQTT client is already connected.');
      return this.client;
    }
    // 如果第一个参数是 IClientOptions 类型，则将其赋值给 opts
    if(typeof brokerUrl === 'object') {
      opts = brokerUrl;
      brokerUrl = ''; // 如果 brokerUrl 是空字符串，mqtt.connect 会使用 opts 中的 brokerUrl
    }

    // 确保 opts 不为空
    opts = opts || {};

    // 调用 mqtt.connect
    this.client = mqtt.connect(brokerUrl, opts);
    this.client.on('connect', () => {
      console.log('Connected to MQTT broker');
    })
    this.client.on('error', (error) => {
      console.error('MQTT error:', error);
    });

    this.client.on('close', () => {
      console.log('Disconnected from MQTT broker');
    });
    return this.client;
  }

  /**
  * 订阅主题
  * @param topic 主题
  * @param callback 消息回调函数
  */
  subscribe(topic: string, callback: (message: any) => void): void {
    if(!this.client) {
      console.error('MQTT client is not connected.');
      return;
    }
    this.client.subscribe(topic, (err) => {
      if(err) {
        console.error('Subscription error:', err);
      } else {
        console.log(`Subscribed to topic: ${topic}`);
      }
    });
    this.client.on('message', (receivedTopic, message) => {
      if(receivedTopic === topic) {
        callback(message);
      }
    })
  }

  unsubscribe(topic: string, callback?: (packet?: mqtt.Packet) => void) {
    if(!this.client) {
      console.error('MQTT client is not connected.');
      return;
    }
    this.client.unsubscribe(topic, (err, packet?) => {
      if(err) {
        console.error('Unsubscription error:', err);
      } else {
        console.log(`Unsubscribed from topic: ${topic}`);
        callback?.(packet)
      }
    });
  }

  /**
  * 发布消息到主题
  * @param topic 主题
  * @param message 消息内容
  */
  publish(topic: string, message: any, callback?: (packet?: mqtt.Packet) => void) {
    if(!this.client) {
      console.error('MQTT client is not connected.');
      return;
    }
    this.client.publish(topic, message, (err, packet) => {
      if(err) {
        console.error('Publish error:', err);
      } else {
        console.log(`Message published to topic: ${topic}`);
        callback?.(packet)
      }
    })
  }

  /**
   * 断开连接
   */
  disconnect() {
    if(this.client) {
      this.client.end();
      this.client = null;
    }
  }
}

结语：

以上是对 mqtt.js 的简单业务封装。当然还有其他的封装方式，只需要满足当前的业务需求即可。