ESP8266 UDP between AP and client not working?

[gcanzalo]

Hi:

MicroPython v1.19.1 on 2022-06-18; ESP module with ESP8266 running on a pair of D1 minis. One is set as an AP:

import socket
import select
import network
from time import sleep, time

import select

ap = network.WLAN(network.AP_IF)
ap.active(True)
ap.ifconfig(('192.168.4.1', '255.255.255.0', '192.168.4.1', '192.168.4.1'))
ap.config(essid = 'esp8266wifi', password = '123456789')

while ap.active() == False:
  sleep(1)
  print('starting...')

print('Connection successful')
print(ap.ifconfig())

sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.bind(('192.168.4.1', 6060))

while True:
    sleep(0.01)
    readable, writeable, exceptional = select.select([sock], [sock], [sock], 1)

    for s in readable:
      print(s.recvfrom(8))

The other as a client:

import socket
import network
from time import sleep, time
wlan = network.WLAN(network.STA_IF)
wlan.active(True)
wlan.ifconfig(('192.168.4.10', '255.255.255.0', '192.168.4.1', '192.168.4.1'))
wlan.connect('esp8266wifi', '123456789')
while not wlan.isconnected():
    print('connecting to network...')
    sleep(1)

print('network config:', wlan.ifconfig())

sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
# sock.bind(('192.168.4.10', 12345))

while True:
    sleep(1)
    print(sock.sendto(b'1', ('192.168.4.1', 6060)))
    print(wlan.ifconfig())

Which doesn't work. The client sends, but the AP doesn't receive the packet. If I uncomment the bind statement in the client script, an EINVAL error is thrown on sendto. The AP receives packets fine from my PC if I run the following:

import socket
from time import sleep, time

sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.bind(('', 6060))

while True:
    sleep(1)
    print(sock.sendto(b'from PC', ('192.168.4.1', 6060)))

What am I doing wrong?

Thank you.

[davefes]

I have found that setting static IPs on the ESP32 needed a short delay, say 0.5 seconds before it. Throwing some try/except blocks around might give you a clue.

[gcanzalo]

I perused several tutorials, all had active() before config(), so I assumed (emphasis on the ass) active() was to be called prior configuration. Not so. Your script should work fine without sleep() simply by moving active() after all configs.

I'm quite pleased with the result, getting ~160 Hz transmission rates of 8 byte packets between these two cheap, little devices! On my way to having a wireless TIG foot pedal!

[davefes]

Do you mind if I elevated this to try and get a common understanding on whether or not you config or make active first? I have spent countless hours trying to get bullet-proof WiFi connections even with hotspots a few metres away.

I am working on an ESP32-CAM and he inits first and then changes camera settings.
A similar camera effort here:
https://randomnerdtutorials.com/esp32-cam-send-photos-email/
inits first and then changes camera settings

As you point out the docs:
https://docs.micropython.org/en/latest/esp32/quickref.html
suggest that making the interface active is the first thing you do.

[gcanzalo]

Elevate away...

[gcanzalo]

This is quite puzzling. I just cleared the flash with esptool, flashed the latest stable micropython, uploaded my script with the ap.active() after the ap.ifconfig(), and the script raised:

OSError: wifi_set_ip_info() failed

Moved ap.active() before ap.ifconfig() and it ran without exception. Then moved the ap.active() back where it was, after ap.ifconfig(), and it again runs fine. WTF?

[davefes]

Unfortunately, I didn't have a try/except around:
sta_if.ifconfig((config.WiFi_device, '255.255.255.0', config.gateway, '8.8.8.8'))
or I might have seen that error. I didn't get the answer I wanted in:
https://github.com/orgs/micropython/discussions/10152