Invalid frame header with Websockets echo example

[wohltat]

When i try the echo.py (websocket example) i can open the webpage (index.html), but the websocket connection fails instantly with the following Error in the Browser:

WebSocket connection to 'ws://192.168.178.67:5000/echo' failed: Invalid frame header

On the micropython side (ESP32) i get the following response:

>>> %Run -c $EDITOR_CONTENT

MPY: soft reboot
Traceback (most recent call last):
  File "microdot.py", line 1211, in dispatch_request
  File "microdot_websocket.py", line 171, in wrapper
  File "<stdin>", line 18, in echo
  File "microdot_websocket.py", line 28, in receive
  File "microdot_websocket.py", line 113, in _read_frame
OSError: [Errno 116] ETIMEDOUT

Any ideas on whats the problem?

[JohannesNeu]

Hi Wohltat,

I get a similar error on an ESP32 with the echo.py (renamed mine to start automatically to main.py) example:

Starting sync server on 0.0.0.0:5000...
GET /echo 400
GET / 200
Traceback (most recent call last):
File "/lib/microdot.py", line 1211, in dispatch_request
File "/lib/microdot_websocket.py", line 171, in wrapper
File "main.py", line 16, in echo
File "/lib/microdot_websocket.py", line 28, in receive
File "/lib/microdot_websocket.py", line 113, in _read_frame
OSError: [Errno 116] ETIMEDOUT
GET /echo 500

Would appreciate any help as well.

EDIT: The odd thing is that all the times this error is mentioned, it is "always" UART or I2C related:

• https://stackoverflow.com/questions/74589629/how-do-i-correct-an-etimedout-error-on-an-esp32
• https://www.reddit.com/r/learnpython/comments/z4huyv/need_help_with_micropython_for_esp32_and_mpu6050/
• https://forum.lvgl.io/t/ft6x36-oserror-with-other-i2c-devices-on-the-same-bus/6719

Yet I see no reason why microdot would use either?

[wohltat]

This seems to be a bug and as i remember it also did not work in CPython.

The echo_async.py example seems to run fine though.
Since you have both asynchronous and synchronous with that, the bug is not that big of a loss.

[JohannesNeu]

Thanks for your reply, async indeed works without a flaw.