Question

如何检查客户端是否已连接？

从Device类示例中，我了解Device是mqtt.Client()返回的实例 mqtt.js有一个连接标记https://github.com/mqttjs/MQTT.js#connected

但是，device.connected给了我undefined

Answer 1

因为它不存在。

DeviceClient {
  publish: [Function],
  subscribe: [Function],
  unsubscribe: [Function],
  end: [Function],
  handleMessage: [Function: bound ],
  updateWebSocketCredentials: [Function],
  getWebsocketHeaders: [Function],
  updateCustomAuthHeaders: [Function],
  simulateNetworkFailure: [Function],
  _events: 
   { connect: [Function],
     close: [Function],
     reconnect: [Function],
     offline: [Function],
     error: [Function],
     message: [Function] },
  _eventsCount: 6 }

虽然你可以听到＆＃34; connect＆＃34;事件并添加＆＃34;已连接＆＃34;属性如下所示

device.on('connect', function() {
   device.connected = true;
});

再次检查DeviceClient，现在就可以了。

DeviceClient {
  publish: [Function],
  subscribe: [Function],
  unsubscribe: [Function],
  end: [Function],
  handleMessage: [Function: bound ],
  updateWebSocketCredentials: [Function],
  getWebsocketHeaders: [Function],
  updateCustomAuthHeaders: [Function],
  simulateNetworkFailure: [Function],
  _events: 
   { connect: [Function],
     close: [Function],
     reconnect: [Function],
     offline: [Function],
     error: [Function],
     message: [Function] },
  _eventsCount: 6,
  connected: true }

Answer 2

在IoT规则引擎中创建规则并收听生命周期事件。设备连接主题将在连接IoT设备时收到消息。

https://docs.aws.amazon.com/iot/latest/developerguide/life-cycle-events.html

Answer 3

我找到了获取当前状态的技巧要在之后监视该状态，您应该使用先前答案中建议的设备连接主题如果您已启用Fleet索引设置确保启用“事物连接”：将事物连接数据包括在事物索引中。

然后，您可以运行搜索（针对特定的Thing或一组事物），并获取每个Thing的连接状态：

`    AWS = require('aws-sdk');
     var iot = new this.AWS.Iot({
                    accessKeyId: this.AccessKeyId,   
                    secretAccessKey: this.SecretAccessKey,
                    //endpoint: this.host,
                    maxResults: 500,
                    region: this.regionData
                    }); 
    var params = {
              queryString: 'shadow.reported.isConnected.connected = *', 
              indexName: 'AWS_Things',
              nextToken: nexttoken 
            };
    iot.searchIndex(params, function(err, data)
    for (const robot of data.things[0])
        connectivity = robot.connectivity.connected;`

注意-上面的代码不是有效的示例，仅用于说明原理注意2-请记住搜索结果出现在页面中，并且需要以这种方式处理

如何从aws-iot-device-sdk获取连接状态

3 个答案: