ESP32 SocketIO Client is not connecting to Flask-SocketIO Server

Question

I'm trying to connect a ESP32 client using SocketIO with a Flask-SocketIO server and it's not getting connected. The server uses SSL. The local server address is https://192.168.1.137:3000.Is the https causing issue here?

The following is the output from the ESP32 in the serial monitor. Note that esp32 successfully connects to the wifi.

> ["myEvent",{"now":95506}]
> [IOc] Disconnected!
> [IOc] Disconnected!
> [IOc] Disconnected!
> ...

Esp32 code:

/*
* WebSocketClientSocketIOack.ino
*/
#include <Arduino.h>
#include <WiFi.h>
#include <WiFiMulti.h>
#include <WiFiClientSecure.h>
#include <ArduinoJson.h>
#include <WebSocketsClient.h>
#include <SocketIOclient.h>
WiFiMulti 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:
 {
 char * sptr = NULL;
 int id = strtol((char *)payload, &sptr, 10);
 USE_SERIAL.printf("[IOc] get event: %s id: %d\n", payload, id);
 if(id) {
 payload = (uint8_t *)sptr;
 }
 DynamicJsonDocument doc(1024);
 DeserializationError error = deserializeJson(doc, payload, length);
 if(error) {
 USE_SERIAL.print(F("deserializeJson() failed: "));
 USE_SERIAL.println(error.c_str());
 return;
 }
 String eventName = doc[0];
 USE_SERIAL.printf("[IOc] event name: %s\n", eventName.c_str());
 // Message Includes a ID for a ACK (callback)
 if(id) {
 // creat JSON message for Socket.IO (ack)
 DynamicJsonDocument docOut(1024);
 JsonArray array = docOut.to<JsonArray>();
 // add payload (parameters) for the ack (callback function)
 JsonObject param1 = array.createNestedObject();
 param1["now"] = millis();
 // JSON to String (serializion)
 String output;
 output += id;
 serializeJson(docOut, output);
 // Send event
 socketIO.send(sIOtype_ACK, output);
 }
 }
 break;
 case sIOtype_ACK:
 USE_SERIAL.printf("[IOc] get ack: %u\n", length);
 break;
 case sIOtype_ERROR:
 USE_SERIAL.printf("[IOc] get error: %u\n", length);
 break;
 case sIOtype_BINARY_EVENT:
 USE_SERIAL.printf("[IOc] get binary: %u\n", length);
 break;
 case sIOtype_BINARY_ACK:
 USE_SERIAL.printf("[IOc] get binary ack: %u\n", 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);
 // }
 WiFiMulti.addAP("ssid", "mypass");
 //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("192.168.1.137", 3000, "/socket.io/?EIO=4");
 // 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 event name
 // Hint: socket.on('event_name', ....
 array.add("myEvent");
 // 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);
 }
}

Server code (Removed unrelated parts):

from flask import Flask, render_template, Blueprint, current_app, request, session, url_for, render_template
from flask_socketio import SocketIO, emit
from threading import Thread
from queue import Queue
import logging
loggerPath = baseUrl + "logs/appLog.log"
os.makedirs(os.path.dirname(loggerPath), exist_ok=True)
with open(loggerPath, "a") as f:
 logging.basicConfig( level=logging.INFO,
 # format='%(asctime)s - %(name)s - %(levelname)s - %(message)s',
 format='%(levelname)s - %(message)s',
 filename=loggerPath
 ) 
bp = Blueprint('audio', __name__, static_folder='static',
 template_folder='templates')
app = Flask(__name__)
async_mode = "threading"
socketio = SocketIO(app, cors_allowed_origins="*", async_mode=async_mode)
@socketio.on('myEvent')
def test_connect(data): 
 logging.info("receiving")
def runApp():
 try:
 certificatePath = os.getenv('BASE_URL')+"SSL/"
 key = certificatePath+"localhost.key"
 certificate = certificatePath+"localhost.crt"
 context = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER)
 context.load_cert_chain(certificate, key)
 ip = socket.gethostbyname(socket.gethostname())
 socketio.run(app, host=ip, port=3000,ssl_context=context)
 except Exception as e:
 logging.error("Exception occurred in: "+__file__, exc_info=True)
q = Queue()
t = Thread(target=wrapper, args=(q, runApp), daemon=True)
t.start()

• jsotola: have you examined the ESP32BasicExample sketch?
• Shyam3089: Above code is from the WebSockets_Generic\examples\esp32\ESP32_WebSocketClientSocketIO\ESP32_WebSocketClientSocketIO.ino

Answer 1

This is version Socketio issue,I have successfully connected . This installed version Werkzeug 2.0.0 Flask 2.3.3 Flask-SocketIO 4.3.1 python-engineio 3.13.2 python-socketio 4.6.0