What Is HTTP

HTTP (HyperText Transfer Protocol) is the most widely used "request-response" protocol on the Internet: a client (your module, browser, or mobile app) sends a request, and the server returns a response. Web browsing, weather queries, and device data reporting mostly run over HTTP.

HTTP is a text protocol — requests and responses are human-readable text lines with a fixed format that is easy to debug. It is not encrypted by itself; when encryption is needed, use HTTPS (HTTP + TLS/SSL, see HTTPS page).

Request

An HTTP request consists of three parts:

Request line: method + space + URL + space + protocol version, for example:

GET /index.html HTTP/1.1

Headers: one "key: value" per line, giving the server extra information, for example:

Host: www.gov.cn
User-Agent: Ai-M62
Content-Type: application/json

Body: optional. GET usually has no body; POST/PUT use it to carry submitted data (forms, JSON, etc.).

Response

The server's response also consists of three parts:

Status line: protocol version + space + status code + space + reason phrase, for example:

HTTP/1.1 200 OK

Response headers: same format as request headers, e.g. Content-Type (content type) and Content-Length (content length).

Response body: the actual content returned by the server (HTML, JSON data, images, etc.).

Common Methods

Method	Meaning	Typical use
GET	Retrieve a resource	Request a web page, query weather, read device state; parameters go in the URL
POST	Submit data	Create a resource: login, report data, publish a message; data goes in the body
PUT	Replace entirely	Replace a resource with the request body
DELETE	Remove a resource	Delete the specified resource on the server

Corresponding tutorials: GET, POST, PUT, DELETE.

Common Status Codes

Code	Meaning	Notes
200	OK	Request succeeded
201	Created	Creation succeeded (common with POST)
301/302	Redirect	The resource moved; the client should follow the redirect
400	Bad Request	Malformed request
401	Unauthorized	Not authenticated
403	Forbidden	No permission
404	Not Found	Resource does not exist
500	Internal Server Error	Server-side error

Relationship with the SDK Example

The Bouffalo SDK example examples/wifi/sta/wifi_http demonstrates issuing HTTP requests from the module: flash the firmware, connect to Wi-Fi, then type wifi_http_test <url> in the serial shell. The example uses the https_client component to send the request and receives/prints the server response through a callback (response_cb).

• Internally the example resolves the hostname to an IP (gethostbyname), opens a TCP connection (port 80), sends the HTTP text, and receives the response via callbacks;
• The four method pages (GET/POST/PUT/DELETE) are all based on this example; the full code and API explanations are on each page;
• HTTPS (encrypted HTTP) is covered in the HTTPS page, backed by the SDK example examples/wifi/sta/wifi_https.

Summary

• HTTP is a text request-response protocol: the client sends "method + URL + headers + body", the server replies with "status code + headers + body";
• GET retrieves data, POST submits data, PUT replaces entirely, DELETE removes;
• Status codes: 2xx success, 3xx redirect, 4xx client error, 5xx server error;
• Before running HTTP on the module, make sure it is connected to Wi-Fi (wifi_sta_connect <ssid> <password>).

Have questions?

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