🛠 Servir une page web depuis la Pico W (socket TCP + HTTP)

Objectives

Once connected to Wi-Fi (connection tutorial), the Pico W is a full network node: it knows how to listen on a TCP port and answer in HTTP. You will write a mini web server with MicroPython's socket module — the same principle as the official picow_httpd example from the pico-examples repository (pico_w/wifi/ folder), in much shorter form. The displayed page can later carry buttons to drive GPIOs: this is the basis of any embedded control interface.

Hardware

• 1 × Raspberry Pi Pico W + _picow MicroPython firmware
• 2.4 GHz Wi-Fi network (the board must be reachable from your PC)
• Serial console at 115200 bauds (to read the IP at startup)
• A web browser on the same network

Full code

# webserver.py — mini serveur HTTP sur la Pico W (MicroPython)
import machine, network, socket, time

def do_connect:
    wlan = network.WLAN
    wlan.active(True)
    if not wlan.isconnected:
        wlan.connect('my_ssid', 'my_password')
        while not wlan.isconnected:
            machine.idle
    print('IP :', wlan.ipconfig('addr4'))

do_connect

addr = socket.getaddrinfo('0.0.0.0', 80)[0][-1]
s = socket.socket
s.bind(addr)
s.listen(1)
print('ecoute sur port 80')
while True:
    cl, remote = s.accept
    req = cl.recv(100)                        # lit la requête HTTP
    print('recu:', req[:40])
    page = (b'HTTP/1.0 200 OK\r\nContent-Type: text/html\r\n\r\n'
            b'<h1>Bonjour depuis ma Pico W</h1>'
            b'<p>Rafrichis-moi !</p>')
    cl.write(page)
    cl.close

Expected verification

The serial console displays the IP (e.g. 192.168.1.42). Pointing the browser at http://192.168.1.42/, the page displays and each reload makes the received request scroll in the console. The CYW43439 can also serve as an access point (SoftAP) with up to 4 clients — in this mode, the Pico W itself distributes the network (documented limit of the chip).

Common errors

• The browser runs on a different network (4G, guest VLAN): the board must be reachable on the same LAN; check the ping before hunting for a bug.
• Blocking accept loop: one connection at a time; if a client keeps the connection open (some browsers preconnect), the following ones wait — add a cl.settimeout or serve fast and close cleanly.
• Forgetting the \r\n in the HTTP header: the browser displays raw text or spins around; the header separator is mandatory.
• recv(100) then full request processing: enough for a simple GET, but do not count on serving files with that — read the request up to the double \r\n\r\n.
• PC firewall blocking, or router with client isolation (AP isolation): two classic causes of "unreachable IP".
• Nothing goes through in SoftAP: the CYW43439 limits the number of clients (4) and your PC must be connected to the network emitted by the board.