Note

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HTTPS Client Example Walkthrough

Example Location

Low-level Socket and TLS version:

• Board firmware path: /sdcard/examples/14-Socket/https_client.py

• SDK source path: src/canmv/resources/examples/14-Socket/https_client.py

requests high-level interface version:

• Board firmware path: /sdcard/examples/14-Socket/https_client2.py

• SDK source path: src/canmv/resources/examples/14-Socket/https_client2.py

Both examples access https://www.baidu.com and are used to compare the differences between manually establishing a TLS connection and using a high-level HTTP client library.

Preparation Before Running

Both scripts use the same common network configuration. Modify the Wi-Fi credentials, or change NETWORK_TYPE to "lan" or "default":

NETWORK_TYPE = "wifi_sta"
WLAN_DEVICE = "auto"
WIFI_SSID = "TEST"
WIFI_PASSWORD = "12345678"
NETWORK_TIMEOUT = 20

The board must be able to access the Internet and resolve DNS. In real applications, if certificate validity period verification is enabled in the TLS configuration, you should also make sure the device time is correct first.

Low-level TLS Version

Resolve and Connect to the HTTPS Port

addr = usocket.getaddrinfo("www.baidu.com", 443)[0][-1]
sock = usocket.socket()
sock.connect(addr)

HTTPS uses TCP port 443 by default. At this point, only the TCP connection has been established; the encrypted channel has not yet been set up.

Wrap the TLS Socket

ssl_sock = ussl.wrap_socket(sock, server_hostname="www.baidu.com")

server_hostname provides SNI during the TLS handshake. When multiple websites share the same IP, the server relies on SNI to select the corresponding certificate and site.

Send the HTTP Request and Read in a Loop

ssl_sock.write(
    b"GET / HTTP/1.1\r\nHost: www.baidu.com\r\nConnection: close\r\n\r\n"
)

while True:
    data = ssl_sock.read()
    if not data:
        break
    print(data.decode(), end="")

The request uses Connection: close, and the read loop ends when the server closes the connection. Finally, ssl_sock.close() is called to release the TLS and TCP resources.

requests high-level version

response = requests.get("https://www.baidu.com")
print(response.text)
response.close()

requests.get() internally handles DNS, TCP, TLS and HTTP processing, suitable for ordinary business requests. After reading the response, you should still explicitly call response.close() to promptly release the Socket and memory.

Running and Troubleshooting

1. When learning for the first time, run https_client2.py first to confirm that the network and HTTPS basic environment are normal.

2. Then run https_client.py to observe the raw HTTP status line, response headers, and body.

3. For DNS errors, check the network, gateway, and DNS; for connection timeouts, check the default uplink and firewall.

4. When the TLS handshake fails, check the system time, target domain name, SNI, and the TLS algorithms supported by the firmware.