Socket.io does not connect

[antoniodynamus]

I'm trying to communicate an ESP8266 with a socket.io server in a JS node. the node.js server is ok, but the library's code is not working.

/*
 * WebSocketClientSocketIO.ino
 *
 *  Created on: 06.06.2016
 *
 */

#include <Arduino.h>

#include <ESP8266WiFi.h>
#include <ESP8266WiFiMulti.h>

#include <ArduinoJson.h>

#include <WebSocketsClient.h>
#include <SocketIOclient.h>

#include <Hash.h>

ESP8266WiFiMulti WiFiMulti;
SocketIOclient socketIO;

#define USE_SERIAL Serial

void socketIOEvent(socketIOmessageType_t type, uint8_t * payload, size_t length) {
    switch(type) {
        case sIOtype_DISCONNECT:
            USE_SERIAL.printf("[IOc] Disconnected!\n");
            break;
        case sIOtype_CONNECT:
            USE_SERIAL.printf("[IOc] Connected to url: %s\n", payload);

            // join default namespace (no auto join in Socket.IO V3)
            socketIO.send(sIOtype_CONNECT, "/");
            break;
        case sIOtype_EVENT:
            USE_SERIAL.printf("[IOc] get event: %s\n", payload);
            break;
        case sIOtype_ACK:
            USE_SERIAL.printf("[IOc] get ack: %u\n", length);
            hexdump(payload, length);
            break;
        case sIOtype_ERROR:
            USE_SERIAL.printf("[IOc] get error: %u\n", length);
            hexdump(payload, length);
            break;
        case sIOtype_BINARY_EVENT:
            USE_SERIAL.printf("[IOc] get binary: %u\n", length);
            hexdump(payload, length);
            break;
        case sIOtype_BINARY_ACK:
            USE_SERIAL.printf("[IOc] get binary ack: %u\n", length);
            hexdump(payload, length);
            break;
    }
}

void setup() {
    // USE_SERIAL.begin(921600);
    USE_SERIAL.begin(115200);

    //Serial.setDebugOutput(true);
    USE_SERIAL.setDebugOutput(true);

    USE_SERIAL.println();
    USE_SERIAL.println();
    USE_SERIAL.println();

      for(uint8_t t = 4; t > 0; t--) {
          USE_SERIAL.printf("[SETUP] BOOT WAIT %d...\n", t);
          USE_SERIAL.flush();
          delay(1000);
      }

    // disable AP
    if(WiFi.getMode() & WIFI_AP) {
        WiFi.softAPdisconnect(true);
    }

    WiFiMulti.addAP("ssid", "passpass");

    //WiFi.disconnect();
    while(WiFiMulti.run() != WL_CONNECTED) {
        delay(100);
    }

    String ip = WiFi.localIP().toString();
    USE_SERIAL.printf("[SETUP] WiFi Connected %s\n", ip.c_str());

    // server address, port and URL
    socketIO.begin("***.***.*.*", 8080);

    // event handler
    socketIO.onEvent(socketIOEvent);
}

unsigned long messageTimestamp = 0;
void loop() {
    socketIO.loop();

    uint64_t now = millis();

    if(now - messageTimestamp > 2000) {
        messageTimestamp = now;

        // creat JSON message for Socket.IO (event)
        DynamicJsonDocument doc(1024);
        JsonArray array = doc.to<JsonArray>();
        
        // add evnet name
        // Hint: socket.on('event_name', ....
        array.add("event_name");

        // add payload (parameters) for the event
        JsonObject param1 = array.createNestedObject();
        param1["now"] = (uint32_t) now;

        // JSON to String (serializion)
        String output;
        serializeJson(doc, output);

        // Send event        
        socketIO.sendEVENT(output);

        // Print JSON for debugging
        USE_SERIAL.println(output);
    }
}

messages that appear in the terminal:

[WS-Client][handleClientData] header response timeout.. disconnecting!
[WS-Client] client disconnected.
[IOc] Disconnected!
[wsIOc] Disconnected!
[WS-Client] connect ws...
[WS-Client] connected to 192.168.1.7:3000.
[WS-Client][sendHeader] sending header...
[WS-Client][sendHeader] handshake GET /socket.io/?EIO=3&transport=polling HTTP/1.1
Host: 192.168.1.7:3000
Connection: keep-alive
Origin: file://
User-Agent: arduino-WebSocket-Client

[write] n: %zu t: 155
[WS-Client][sendHeader] sending header... Done (14751us).
[WS-Client][handleHeader] RX: HTTP/1.1 400 Bad Request
[WS-Client][handleHeader] RX: Content-Type: application/json
[WS-Client][handleHeader] RX: Date: Tue, 23 Feb 2021 05:44:59 GMT
[WS-Client][handleHeader] RX: Connection: keep-alive
[WS-Client][handleHeader] RX: Transfer-Encoding: chunked
[WS-Client][handleHeader] Header read fin.
[WS-Client][handleHeader] Client settings:
[WS-Client][handleHeader]  - cURL: /socket.io/?EIO=3
[WS-Client][handleHeader]  - cKey: /IuVcv2lO1JxNyopQv6pTA==
[WS-Client][handleHeader] Server header:
[WS-Client][handleHeader]  - cCode: 400
[WS-Client][handleHeader]  - cIsUpgrade: 0
[WS-Client][handleHeader]  - cIsWebsocket: 0
[WS-Client][handleHeader]  - cAccept: 
[WS-Client][handleHeader]  - cProtocol: arduino
[WS-Client][handleHeader]  - cExtensions: 
[WS-Client][handleHeader]  - cVersion: 0
[WS-Client][handleHeader]  - cSessionId: 
[WS-Client][handleHeader] still missing cSessionId try socket.io V3
[WS-Client][handleHeader] socket.io json: 33
{"code":5,"message":"Unsupported protocol version"}
0
[WS-Client][handleHeader] RX: 33
{"code":5,"message":"Unsupported protocol version"}
0

[Links2004]

you can try this change with the latest version of the lib:

    socketIO.begin("***.***.*.*", 8080,"/socket.io/?EIO=4");