问 使用PubSubClient.h回调函数的NodeMCU esp8266被忽略

EN

已解决的

我发布的代码和@karan发布的代码都是正确的。我遇到的问题是通过thingspeak代理连接和Thingspeak文档实现的，当时还没有更新。尤其是需要传递MQTT_APIKEY和用户名来建立与mqtt broker连接，即使使用公共通道也是如此。

在连接步骤中传递这两个参数即可解决问题，如下所示：

    client.connect("ESP8266Client-", "Your_username", "MQTT_APIKEY");

非常感谢@karan帮助我，并改进了我的代码。

您正在订阅的主题与要发布到的主题不同。您的发布主题是"channels/517055/publish/V4ZW4Y01ZLFD5XYR“，而您订阅的是”channels/517055/subscribe/field4/field4“。

实际上，您的代码几乎是正确的，但是loop()函数正在无限地执行。基本上，代码卡在循环函数中，这就是它不能订阅的原因。即使它也被订阅，循环函数也将控制回调函数，回调函数将不会被调用，它将充当NULL

这是代码，我做了一些修改。试试看吧

**此代码不会每次都发布有效负载，如果需要，您可以在client.loop()之前添加循环中的client.plublish ()。

#include <ESP8266WiFi.h>
#include <PubSubClient.h>
// Update these with values suitable for your network.
const char* ssid = "*****";
const char* password = "*****";
const char* mqtt_server = "mqtt.thingspeak.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("Ciao sono la callback1\n");
  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') {
    Serial.print("Ciao sono la callback2\n");
    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 acive low on the ESP-01)
  } else {
    Serial.print("Ciao sono la callback3\n");
    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("channels/517055/publish/V4ZW4Y01ZLFD5XYR", "field5=7&status=MQTTPUBLISH");
      // ... and resubscribe
      client.subscribe("channels/517055/subscribe/fields/field4");
      Serial.print("Ciao sono subscribe 01\n");
    } 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);
  Serial.print("Ciao sono la callback 10\n");
  connectmqtt();
void loop() {
  if (!client.connected()) {
    reconnect();
  long now = millis();
  if (now - lastMsg > 2000) {
    lastMsg = now;
    ++value;
    snprintf (msg, 75, "field4= %ld&status=MQTTPUBLISH", value);
    Serial.print("Publish message: ");
    Serial.println(msg);
     client.loop();
void connectmqtt()
  client.connect("ESP8266Client-");
      Serial.println("connected");
      // Once connected, publish an announcement...
      // ... and resubscribe
      client.subscribe("channels/517055/subscribe/fields/field4");
       client.publish("channels/517055/publish/V4ZW4Y01ZLFD5XYR", msg);