HTTP

The undelying network protocol for communication on the web. It defines methods like GET, POST, PUT, and DELETE.
When you visit a website, your browser sends HTTP requests and the server sends back HTTP responses.

HTTP 消息是客户端和服务器之间通信的基础，它们由一系列的文本行组成，遵循特定的格式和结构。
HTTP消息分为两种类型：请求消息和响应消息。
一个 HTTP 客户端是一个应用程序（Web 浏览器或其他任何客户端），通过连接到服务器达到向服务器发送一个或多个 HTTP 的请求的目的。
一个 HTTP 服务器同样也是一个应用程序（通常是一个 Web 服务，如 Nginx、Apache 服务器或 IIS 服务器等），通过接收客户端的请求并向客户端发送 HTTP 响应数据。

Client Side Request

请求行（Request Line）：

方法：如 GET、POST、PUT、DELETE等，指定要执行的操作。
请求 URI（统一资源标识符）：请求的资源路径，通常包括主机名、端口号（如果非默认）、路径和查询字符串。
HTTP 版本：如 HTTP/1.1 或 HTTP/2。
请求行的格式示例：GET /index.html HTTP/1.1

请求头（Request Headers）：

包含了客户端环境信息、请求体的大小（如果有）、客户端支持的压缩类型等。
常见的请求头包括Host、User-Agent、Accept、Accept-Encoding、Content-Length等。

空行：

请求头和请求体之间的分隔符，表示请求头的结束。

请求体（可选）：

在某些类型的HTTP请求（如 POST 和 PUT）中，请求体包含要发送给服务器的数据。

Server Side Response

状态行（Status Line）：

HTTP 版本：与请求消息中的版本相匹配。
状态码：三位数，表示请求的处理结果，如 200 表示成功，404 表示未找到资源。
状态信息：状态码的简短描述。
状态行的格式示例：HTTP/1.1 200 OK

响应头（Response Headers）：

包含了服务器环境信息、响应体的大小、服务器支持的压缩类型等。
常见的响应头包括Content-Type、Content-Length、Server、Set-Cookie等。

空行：

响应头和响应体之间的分隔符，表示响应头的结束。

响应体（可选）：

包含服务器返回的数据，如请求的网页内容、图片、JSON数据等。

FormData

multipart/form-data is an encoding type (media or content type) used in HTTP requests to send data to a server, primarily for forms that include file uploads.
In HTML, you specify this encoding by setting the enctype attribute of the <form> tag to multipart/form-data when the method is POST. This is mandatory if your form includes an <input type=”file”> element.

<form action="/upload" method="post" enctype="multipart/form-data">
  <input type="text" name="username" />
  <input type="file" name="profile_picture" />
  <button type="submit">Upload</button>
</form>

When using modern web APIs like the Fetch API or XMLHttpRequest in JavaScript, the browser’s FormData object automatically handles the complex process of structuring the request in the multipart/form-data format.
WWWForm is a Unity class used to create a standard web form. It structures data into the multipart/form-data or x-www-form-urlencoded format, which is a standard format for submitting form data, including file uploads, to web servers.

REST API

A set of architectural constraints (like statelessness and uniform interface) that define how to build scalable and standardized web services, primarily using HTTP.
Guidelines for designing a server’s endpoints in a logical, resource-oriented way, specifically origanize resources in URIs like https://exmaple.com/api/v3/users
For example, a REST API would use GET /users to retrieve users, POST /users to create a new user, and leverage standard HTTP status codes.

Fetch API

A modern, promise-based JavaScript interface built into web browsers that allows developers to make HTTP requests programmatically.
Client-side tool used to consume a service that might be RESTful (or any other kind of HTTP API).
You use the Fetch API in JavaScript in your web browser or a server environment like Node.js to send the HTTP requests defined by the API’s design.

In summary, you use the Fetch API to send HTTP requests to a server that is structured as a REST API.

XHR

XML Http Request (XHR) is a JavaScript API to create HTTP requests. Its methods provide the ability to send network requests between the browser and a server. The Fetch API is the modern replacement for XMLHttpRequest

ASP.NET

Microsoft’s open-source framework for building web applications and and services using .NET and C#; it is fundamentally built on top of the HTTP protocol.

HTTP/2 & HTTP/3: Modern versions of ASP.NET Core support HTTP/2 and HTTP/3 for improved performance.
Status Codes: The framework provides built-in methods to return standard HTTP status codes, such as Ok() (200), CreatedAtAction() (201), or NotFound() (404).

Handling Incoming HTTP Requests (Server-Side)

HTTP Servers: ASP.NET Core uses Kestrel, a cross-platform HTTP server, as the default to listen for requests.
HttpContext: Every request is encapsulated in an HttpContext object, which provides access to the Request (headers, body, query strings) and the Response.
Routing and HTTP Methods: Controllers use attributes like [HttpGet], [HttpPost], and [HttpPut] to map specific HTTP verbs to C# methods.

Creating an HTTP Endpoint

var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();

// Simple GET endpoint returning a string
app.MapGet("/", () => "Hello World!");

// GET endpoint with a route parameter
app.MapGet("/products/{id}", (int id) => $"Returning product {id}");

// POST endpoint that accepts a JSON object (Todo item)
app.MapPost("/todoitems", (Todo todo) => 
    Results.Created($"/todoitems/{todo.Id}", todo));

app.Run();

// Data model for the POST example
public record Todo(int Id, string Name, bool IsComplete);

Making Outgoing Requests (Client-Side)

To consume other web services or APIs from within your ASP.NET application, you use the HttpClient class.

Controller or Page Model

public class MyService
{
    private readonly IHttpClientFactory _httpClientFactory;

    public MyService(IHttpClientFactory httpClientFactory)
    {
        _httpClientFactory = httpClientFactory;
    }

    public async Task<string> GetExternalDataAsync()
    {
        // 1. Create the client
        var client = _httpClientFactory.CreateClient();

        // 2. Make the GET request
        var response = await client.GetAsync("https://api.example.com");

        // 3. Ensure success and read content
        if (response.IsSuccessStatusCode)
        {
            return await response.Content.ReadAsStringAsync();
        }

        return "Error fetching data";
    }
}

Credits

https://www.runoob.com/http/http-messages.html

乌啦呀哈呀哈乌啦！

HTTP and ASP.NET