MQTT.js订阅从
问题描述：
我上CloudMQTT运行代理收到同一消息的倍数和我的JS代码如下所示：MQTT.js订阅从
var mqtt_url = URL.parse('mqtt://m10.cloudmqtt.com:15272' || 'mqtt://localhost:1883');
var auth = (mqtt_url.auth || ':').split(':');
var url = "mqtt://" + mqtt_url.host;
var options = {
port: mqtt_url.port,
clientId: 'mqttjs_' + Math.random().toString(16).substr(2, 8),
username: USERNAME,
password: PASSWORD,
};
// Create a client connection
var client = mqtt.connect(url, options);
client.on('connect', function() { // When connected
// subscribe to a topic
client.subscribe('relay', function() {
// when a message arrives, do something with it
client.on('message', function(topic, message, packet) {
// console.log(packet);
console.log("Received '" + message + "' on '" + topic + "'");
});
});
// subscribe to a topic
client.subscribe('photoresistor', function() {
// when a message arrives, do something with it
client.on('message', function(topic, message, packet) {
console.log("Received '" + message + "' on '" + topic + "'");
});
});
// publish a message to a topic
client.publish('relay', value, function() {
console.log("Message of ", value, " is published");
// client.end(); // Close the connection when published
});
});
我有我的ESP8266迷上了光敏电阻，它出版光敏电阻值为photoresistor，每5秒一次。
那么，我每5秒钟就会在我的节点服务器（MeteorJS）上得到四个相同的控制台日志。
I20170907-19:33:51.421(-4)? Received '156' on 'photoresistor'
I20170907-19:33:51.423(-4)? Received '156' on 'photoresistor'
I20170907-19:33:51.424(-4)? Received '156' on 'photoresistor'
I20170907-19:33:51.425(-4)? Received '156' on 'photoresistor'
I20170907-19:33:57.741(-4)? Received '39' on 'photoresistor'
I20170907-19:33:57.742(-4)? Received '39' on 'photoresistor'
I20170907-19:33:57.743(-4)? Received '39' on 'photoresistor'
I20170907-19:33:57.743(-4)? Received '39' on 'photoresistor'
I20170907-19:34:05.465(-4)? Received '37' on 'photoresistor'
I20170907-19:34:05.467(-4)? Received '37' on 'photoresistor'
I20170907-19:34:05.468(-4)? Received '37' on 'photoresistor'
I20170907-19:34:05.470(-4)? Received '37' on 'photoresistor'
I20170907-19:34:10.665(-4)? Received '161' on 'photoresistor'
I20170907-19:34:10.667(-4)? Received '161' on 'photoresistor'
I20170907-19:34:10.667(-4)? Received '161' on 'photoresistor'
I20170907-19:34:10.668(-4)? Received '161' on 'photoresistor'
任何想法可能导致client.subscribe功能或CloudMQTT对同一消息的输出倍数？
答
看起来在某些情况下，订阅连接事件处理程序内部可能会导致重复订阅。 mqtt.js release 2.9.0解决了这种性质的问题，如所述。 因此，升级到最新的mqtt.js版本（目前是2.13.1）可能会解决您的问题。
但是，请注意，mqtt.js usage notes指出“从v2.0.0开始，订阅在重新连接时会恢复，如果clean：true”。另见here。如果是这样的话，您似乎根本不需要在连接事件处理程序中进行订阅，这应该有望避免首先发生重复订阅。
您应该可以测试上述假设，只需在您的node.js客户端连接时重新启动CloudMQTT代理即可。这是否会导致您开始看到重复的消息？如果是这样，我相信补救措施的确是简单地将您的订阅移到连接事件处理程序之外。
您是否使用其他客户端（例如mosquitto_sub）检查是否有多个消息正在发布？ – hardillb
你有没有到过这个底部？我看到完全相同的问题。有任何想法吗？ –