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I released https://github.com/Links2004/arduinoWebSockets/releases/tag/2.3.4 that will make it easier for platformio

can you post the log for 2.3.4 with the `found EIO=4 disable EIO ping on client`

ok, thanks, are you sure that your data string is correct for me it looks like you include the `engineIO` and `socketIO` message types (the numbers) which will be included...

I do not own a W5500, but since the API is the same (`Ethernet.h`) as for the W5100 you can try to set the `WEBSOCKETS_NETWORK_TYPE` define to `NETWORK_W5100`.

you can try this change with the latest version of the lib: ```cpp socketIO.begin("***.***.*.*", 8080,"/socket.io/?EIO=4"); ```

can you verify that its the lib an not the TCP stack? simply create a TCP server / client on open a connection.

and a bit more detail about you setup will help to get a idea about you setup. are you using the lib in websocket server mode? is the ESP running...

`cleanupClients` simply force closes a connections, noting special here. https://github.com/me-no-dev/ESPAsyncWebServer/blob/master/src/AsyncWebSocket.cpp you can use disconnect to kill all or once specific client via: https://github.com/Links2004/arduinoWebSockets/blob/900d81e5345fe2dbe74fd175749c80e2bbda2f00/src/WebSocketsServer.h#L80-L81 heartbeat can be configured via: https://github.com/Links2004/arduinoWebSockets/blob/900d81e5345fe2dbe74fd175749c80e2bbda2f00/src/WebSocketsServer.h#L90-L91 and...

this lib can connect to any port you like, see port variable here: https://github.com/Links2004/arduinoWebSockets/blob/f55bf8d4ededd2d7acf36788e5cfe6e6393dd235/src/WebSocketsClient.h#L41-L43 same goes for the server, you can start it at any port: https://github.com/Links2004/arduinoWebSockets/blob/f55bf8d4ededd2d7acf36788e5cfe6e6393dd235/src/WebSocketsServer.h#L221

please decode the stack Exception, the memory is different for each build you make so no way to help you without decoding. https://arduino-esp8266.readthedocs.io/en/latest/Troubleshooting/stack_dump.html