MQTT 客户端打开新连接，然后关闭它们答案

【问题标题】：MQTT client opens new connections, then closes themMQTT 客户端打开新连接，然后关闭它们
【发布时间】：2021-12-29 20:08:33
【问题描述】：

这显示在蚊子日志中：

1636686996: New connection from 192.168.1.10:58779 on port 1884.
1636686996: New connection from 192.168.1.10:52435 on port 1884.
1636686996: New connection from 192.168.1.10:53212 on port 1884.
1636686996: New connection from 192.168.1.10:52612 on port 1884.
1636686996: New connection from 192.168.1.10:60982 on port 1884.
1636686996: New connection from 127.0.0.1:61362 on port 1884.
1636686996: New connection from 192.168.1.10:64731 on port 1884.
1636686996: Client mqtt_0dd8eeee22c90b58 closed its connection.
1636686996: New client connected from 192.168.1.10:55946 as ESP8266Client-1bdf (p2, c1, k15).
1636686996: No will message specified.
1636686996: Sending CONNACK to ESP8266Client-1bdf (0, 0)
1636686996: New client connected from 192.168.1.10:58779 as ESP8266Client-190f (p2, c1, k15).
1636686996: No will message specified.
1636686996: Sending CONNACK to ESP8266Client-190f (0, 0)
1636686996: New client connected from 192.168.1.10:60982 as ESP8266Client-c6b0 (p2, c1, k15).
1636686996: No will message specified.
1636686996: Sending CONNACK to ESP8266Client-c6b0 (0, 0)
1636686996: New client connected from 127.0.0.1:61362 as mqtt_0dd8eeee22c90b58 (p2, c1, k60).
1636686996: No will message specified.
1636686996: Sending CONNACK to mqtt_0dd8eeee22c90b58 (0, 0)
1636686996: New client connected from 192.168.1.10:64731 as ESP8266Client-3a80 (p2, c1, k15).
1636686996: No will message specified.
1636686996: Sending CONNACK to ESP8266Client-3a80 (0, 0)
1636686996: Client ESP8266Client-1bdf closed its connection.
1636686996: Client ESP8266Client-190f closed its connection.
1636686996: Client ESP8266Client-5bbf closed its connection.

客户端代码：

#include <ESP8266WiFi.h>
#include <PubSubClient.h>

// Update these with values suitable for your network.

const char * ssid = "........";
const char * password = "........";
const char * mqtt_server = "broker.mqtt-dashboard.com";

WiFiClient espClient;
PubSubClient client(espClient);
long lastMsg = 0;
char msg[50];
int value = 0;

void setup_wifi() {

  delay(10);
  // We start by connecting to a WiFi network
  Serial.println();
  Serial.print("Connecting to ");
  Serial.println(ssid);

  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }

  randomSeed(micros());

  Serial.println("");
  Serial.println("WiFi connected");
  Serial.println("IP address: ");
  Serial.println(WiFi.localIP());
}

void callback(char * topic, byte * payload, unsigned int length) {
  Serial.print("Message arrived [");
  Serial.print(topic);
  Serial.print("] ");
  for (int i = 0; i < length; i++) {
    Serial.print((char) payload[i]);
  }
  Serial.println();

  // Switch on the LED if an 1 was received as first character
  if ((char) payload[0] == '1') {
    digitalWrite(BUILTIN_LED, LOW); // Turn the LED on (Note that LOW 
    is the voltage level
    // but actually the LED is on; this is because
    // it is active low on the ESP-01)
  } else {
    digitalWrite(BUILTIN_LED, HIGH); // Turn the LED off by making the 
    voltage HIGH
  }

}

void reconnect() {
  // Loop until we're reconnected
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection...");
    // Create a random client ID
    String clientId = "ESP8266Client-";
    clientId += String(random(0xffff), HEX);
    // Attempt to connect
    if (client.connect(clientId.c_str())) {
      Serial.println("connected");
      // Once connected, publish an announcement...
      client.publish("outTopic", "hello world");
      // ... and resubscribe
      client.subscribe("inTopic");
    } else {
      Serial.print("failed, rc=");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");
      // Wait 5 seconds before retrying
      delay(5000);
    }
  }
}

void setup() {
  pinMode(BUILTIN_LED, OUTPUT); // Initialize the BUILTIN_LED pin 
  as an output
  Serial.begin(115200);
  setup_wifi();
  client.setServer(mqtt_server, 1883);
  client.setCallback(callback);
}

void loop() {

  if (!client.connected()) {
    reconnect();
  }
  client.loop();

  long now = millis();
  if (now - lastMsg > 2000) {
    lastMsg = now;
    ++value;
    snprintf(msg, 50, "hello world #%ld", value);
    Serial.print("Publish message: ");
    Serial.println(msg);
    client.publish("outTopic", msg);
  }
}

我正在使用 pubsubclient 库。我不知道是网络问题还是 nodemcu 问题。

【问题讨论】：

日志显示连接进入，被确认然后关闭（由客户端）；如果没有更多信息，就不可能告诉你为什么会这样。请编辑问题并添加您的客户代码 (simplify it as much as possible)。
串口输出显示什么？也是来自多个设备的日志还是只有一个？最好一次测试一个，我建议您将客户端 ID 生成移动到 setup()，以便它在设备的正常运行时间内保持稳定，以便更容易跟踪。
串行输出多次显示“Attempting MQTT connection...”。只有两个客户端，一个是连接到代理的 esp8266，自连接后随机 ID 更改，另一个是节点红色客户端。
请edit这个问题显示实际的串行输出而不是解释，我想看看延迟reconnect()函数是否真的发生了，因为要让6个客户端在同一秒内全部连接从你说的是单个设备意味着它不是。

标签： mqtt esp8266 mosquitto

【解决方案1】：

如果没有更多信息，我们无法判断。

我多次遇到同样的问题，原因是：

客户端/服务器的互联网连接很差，因此它一次又一次地重新连接。

在处理实时应用程序时，连接数非常多，因此死/弱连接会自动断开。
不知道为什么，但是如果我连接手机的 wifi（只有 1 部特定手机），连接就会变得奇怪。

【讨论】：