ESP32 Arduino无法连接NodeJS SocketIO WebSocket问题求助

问题背景 #

ESP32已成功连接WiFi，能通过HTTP读取服务器页面内容，但无法建立Socket.IO WebSocket连接，串口反复输出断开信息。开发环境为CLion + PlatformIO Arduino。

ESP32原代码 #

#include <Arduino.h>
#include <WebSocketsClient.h>
#include <HTTPClient.h>

WebSocketsClient websocket;
boolean connected = false;  // 原代码此处缺少分号

void webSocketEvent(WStype_t type, uint8_t * payload, size_t length) {
    switch(type) {
        case WStype_DISCONNECTED:
            Serial.printf("[WSc] Disconnected!\n");
            connected = false;
            break;
        case WStype_CONNECTED: 
            digitalWrite(MESSAGE_LED_PIN, HIGH);  // 原代码未定义MESSAGE_LED_PIN
            Serial.printf("[WSc] Connected to url: %s\n", payload);
            connected = true;
            break;  // 原代码缺少break
    }
}  // 原代码缺少函数闭合的}

void setup() {
    Serial.begin(115200);
    WiFi.begin("SSID", "PASSW");
    while (WiFi.status() != WL_CONNECTED) {
        delay(500);
        Serial.print(".");
    }
    Serial.println("");
    Serial.println("Connesso al WiFi");
    Serial.println(WiFi.localIP());
    inviaRichiestaHTTP(); // 未提供该函数代码
    websocket.begin("192.168.1.16",3000,"/socket.io/?EIO=4");
    websocket.onEvent(webSocketEvent);
}

void loop() {
    websocket.loop();
}

串口输出 #

....
Connesso al WiFi
192.168.1.170
[HTTP] Codice di stato: 200
<h1>Hello world</h1>
[WSc] Disconnected!
[WSc] Disconnected!
[WSc] Disconnected!

Node.js原服务器代码 #

const ip = require("ip");
var app = require('express')();
var server = require('http').createServer(app);
var io = require('socket.io')(server); //pass a http.Server instance
var port = process.env.PORT || 80;

app.get('/', function (req, res) {
    //check sender ip
    var senderip = req.headers['x-forwarded-for'] || req.connection.remoteAddress;
    console.log('sender ip: '+senderip);
   res.send('<h1>Hello world</h1>');
});

io.on('connection', function (socket) {
    console.log('Client connected');
    socket.on('message', function (data) {
        console.log('Message received: ', data);
    });
    socket.on('disconnect', function () {
        console.log('Client disconnected');
    });
});

server.listen(port);

问题排查与解决方法 #

1. 端口不匹配 #

Node.js服务器监听80端口（port = process.env.PORT || 80），但ESP32连接的是3000端口，端口不一致直接导致连接失败。

• 修正：要么把Node.js服务器端口改为3000，要么将ESP32的连接端口改为80，确保两端端口一致。

2. Socket.IO协议兼容性 #

WebSocketsClient是标准WebSocket客户端库，而Socket.IO是基于WebSocket的自定义协议，包含额外的握手和数据包格式，标准WebSocket客户端无法直接兼容。

• 替换为ESP32专用的Socket.IO客户端库，比如PlatformIO中的SocketIoClient库，直接搜索安装即可使用。

3. ESP32代码语法错误 #

原代码存在3处语法错误，会导致运行异常：

• boolean connected = false 末尾缺少分号；
• webSocketEvent函数未闭合（缺少}）；
• MESSAGE_LED_PIN未定义，需提前用#define MESSAGE_LED_PIN 2声明引脚。

修正后的示例代码 #

ESP32代码（使用SocketIoClient库）

#include <Arduino.h>
#include <WiFi.h>
#include <SocketIoClient.h>

#define MESSAGE_LED_PIN 2  // 定义LED引脚
SocketIoClient socketIO;

void setup() {
  Serial.begin(115200);
  pinMode(MESSAGE_LED_PIN, OUTPUT);
  
  WiFi.begin("SSID", "PASSW");
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("\nConnesso al WiFi");
  Serial.println(WiFi.localIP());

  // 连接Socket.IO服务器，端口与服务器保持一致
  socketIO.begin("192.168.1.16", 80);
  
  // 监听连接事件
  socketIO.on("connect", []() {
    Serial.println("[SocketIO] 已成功连接");
    digitalWrite(MESSAGE_LED_PIN, HIGH);
  });
  
  // 监听断开事件
  socketIO.on("disconnect", []() {
    Serial.println("[SocketIO] 连接已断开");
    digitalWrite(MESSAGE_LED_PIN, LOW);
  });
}

void loop() {
  socketIO.loop();
}

Node.js服务器代码（明确端口并添加启动日志）

const app = require('express')();
const server = require('http').createServer(app);
const io = require('socket.io')(server);
const port = 80;  // 明确使用80端口

app.get('/', function (req, res) {
  const senderip = req.headers['x-forwarded-for'] || req.connection.remoteAddress;
  console.log('sender ip: ' + senderip);
  res.send('<h1>Hello world</h1>');
});

io.on('connection', function (socket) {
  console.log('Client connected');
  socket.on('message', function (data) {
    console.log('Message received: ', data);
  });
  socket.on('disconnect', function () {
    console.log('Client disconnected');
  });
});

server.listen(port, () => {
  console.log(`服务器运行在端口 ${port}`);
});

内容的提问来源于stack exchange，提问作者Ivan Cisternino