I need to run a websocket server on ESP32 and the official example raises the following exception when I connect from any client:

MPY: soft reboot
Network config: ('192.168.0.200', '255.255.255.0', '192.168.0.1', '8.8.8.8')
b'Sec-WebSocket-Version: 13\r\n'
b'Sec-WebSocket-Key: k5Lr79cZgBQg7irI247FMw==\r\n'
b'Connection: Upgrade\r\n'
b'Upgrade: websocket\r\n'
b'Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits\r\n'
b'Host: 192.168.0.200\r\n'
b'\r\n'
Finished webrepl handshake
Task exception wasn't retrieved
future: <Task> coro= <generator object 'echo' at 3ffe79b0>
Traceback (most recent call last):
  File "uasyncio/core.py", line 1, in run_until_complete
  File "main.py", line 22, in echo
  File "uasyncio/websocket/server.py", line 60, in WSReader
AttributeError: 'Stream' object has no attribute 'ios'

My micropython firmware and libraries:

• Micropython firmware: https://micropython.org/resources/firmware/esp32-idf3-20200902-v1.13.bin
• Pip libraries installed: micropython-ulogging, uasyncio.websocket.server

My main.py:

import network
import machine

sta_if = network.WLAN(network.STA_IF)
sta_if.active(True)
sta_if.ifconfig(('192.168.0.200', '255.255.255.0', '192.168.0.1', '8.8.8.8'))
if not sta_if.isconnected():
    print('connecting to network...')
    sta_if.connect('my-ssid', 'my-password')
    while not sta_if.isconnected():
        machine.idle() # save power while waiting
print('Network config:', sta_if.ifconfig())

# from https://github.com/micropython/micropython-lib/blob/master/uasyncio.websocket.server/example_websock.py
import uasyncio
from uasyncio.websocket.server import WSReader, WSWriter

def echo(reader, writer):
    # Consume GET line
    yield from reader.readline()

    reader = yield from WSReader(reader, writer)
    writer = WSWriter(reader, writer)

    while 1:
        l = yield from reader.read(256)
        print(l)
        if l == b"\r":
            await writer.awrite(b"\r\n")
        else:
            await writer.awrite(l)


import ulogging as logging
#logging.basicConfig(level=logging.INFO)
logging.basicConfig(level=logging.DEBUG)
loop = uasyncio.get_event_loop()
loop.create_task(uasyncio.start_server(echo, "0.0.0.0", 80))
loop.run_forever()
loop.close()