🛠 Serveur web de commande d'une LED en MicroPython

Objectives

Run a mini HTTP server on the ESP8266 with MicroPython, without any external libraries: we directly use the socket module to accept TCP connections on port 80, parse the request line, and return an HTML page with two links that turn the onboard LED GPIO2 on and off. This tutorial shows another way to program the chip (the MicroPython esp8266 port is very lightweight), the active-LOW principle of the GPIO2 LED (value 0 = on), and retrieving the IP via ifconfig. To be done from a computer on the same network as the module.

Hardware

• 1 ESP8266-ESP-12E module (or NodeMCU) with MicroPython flashed (esp8266 port, "generic-esp8266" binary)
• 1 micro-USB/USB cable or serial adapter for flashing and the IDE (Thonny recommended)
• Onboard LED GPIO2 (or external LED + 330 Ω resistor)
• 2.4 GHz Wi-Fi network and a browser on the same network

Complete code

# main.py MicroPython (port esp8266) - serveur LED sur GPIO2
import network
import socket

led = network and __import__("machine").Pin(2, 1)  # GPIO2 en sortie

sta = network.WLAN(network.STA_IF)
sta.active(True)
if not sta.isconnected:
    sta.connect("mon-reseau", "mot-de-passe")
    import time
    for _ in range(40):
        if sta.isconnected:
            break
        time.sleep_ms(250)
print("IP =", sta.ifconfig[0])

html = ("<h1>ESP-12E</h1>"
        "<a href='/on'><button>ALLUMER</button></a> "
        "<a href='/off'><button>ETEINDRE</button></a>")

def handle(req):
    if req.startswith("GET /on"):        # LED active-LOW : 0 = allumee
        led.value(0)
    elif req.startswith("GET /off"):
        led.value(1)
    return html

s = socket.socket
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind(("0.0.0.0", 80))
s.listen(1)
while True:
    cl, _ = s.accept
    req = cl.recv(100).decode
    cl.send("HTTP/1.0 200 OK\r\nContent-type: text/html\r\n\r\n" + handle(req))
    cl.close

Note: the pin initialization line can also be written cleanly as import machine; led = machine.Pin(2, machine.Pin.OUT) if you paste the code into a real main.py file.

Expected verification

After startup, the console displays the module's IP (for example 192.168.1.57). Open this address in a browser on the same network: the page with two buttons appears. "TURN ON" sets the GPIO2 pin to off (value 0) and turns on the onboard LED; "TURN OFF" does the opposite. The module must remain responsive after several clicks.

Common errors

• Confusing the logic: on the onboard LED, led.value(0) turns it on and led.value(1) turns it off (active-LOW), the opposite of what one intuitively expects.
• The browser displays "connection reset" for the favicon.ico icon: this is normal, the /favicon.ico request falls into the same handler; it simply returns the page.
• Only one client at a time with listen(1): if a connection remains open, the next browser waits; always keep cl.close.
• Forgetting that port 80 must be free: some corporate networks block it; test on a home router.
• Overwriting main.py during execution: the server restarts, this is normal in development, stop the code with Ctrl-C in the IDE before reloading.