Awesome

Micropython-DNSServer-Captive-Portal

This is MicroPython script that creates a Wifi AP with both a DNS and Web Server that act as a 'Captive Portal' by returning its own IP to all DNS queries in an attempt to force connecting clients to its Web Server on port 80.
When connecting from an Android phone it should automatically prompt you to 'Sign in to the network', which, if clicked, redirects to the Web Server. If you try browsing to a random domain it should redirect you to the web server however if the request was HTTPS you will just get a Connected Refused error.

The code is based on several other examples of a MicroPython Captive Portal that I found on Github however they were 1+ years old and relied on a single loop to accept connection for both the DNS and Web servers:

My version uses asyncio to separate the servers and so can be easily extended with additional tasks. Performance and reliability seem better as well.

This was tested with an ESP32 using the latest firmware from https://micropython.org/download#esp32.
The specific version I tested with was esp32-20190805-v1.11-187-g00e7fe8ab.bin.
This should work with an ESP8266 and others as well but I have not fully tested it.

Initial Setup (ESP32 only)

Since asyncio is not included in the binary for the ESP32 however it must be installed first.
Unless you prefer to build your own binary, this requires that your ESP be able to connect to the internet to install.

Open a python terminal with the ESP32 and use the below to connect to your preferred network:

import network
sta_if = network.WLAN(network.STA_IF)
sta_if.active(True)
sta_if.connect('yourssid', 'yourpw')

Then run:

import upip
upip.install('micropython-uasyncio')

To Do

I'd like to be able to serve HTTPS as well, which would make this a lot more useful however I was unable to get the Micropython example code working https://github.com/micropython/micropython/blob/master/examples/network/http_server_ssl.py