ASP.Net最小Web API

最近需要搭建一个Windows Web服务器，处理一些很简单的访问请求，于是研究了一下ASP.Net的最小Web API

项目创建

打开VS2022，按照ASP.Net模块后，使用模板创建项目

程序运行

模板是一个预测（随机生成）未来五天天气的demo，可以用命令行启动程序

dotnet run --project=./项目名称

Mini API

模板项目内容非常少，只有一个C#文件

var builder = WebApplication.CreateBuilder(args);

var app = builder.Build();

// 创建一个Get接口，返回天气预测结果
app.MapGet("/weatherforecast", () =>
{
    var forecast = Enumerable.Range(1, 5).Select(index =>
        new WeatherForecast
        (
            ...
        ))
        .ToArray();
    return forecast;
});

app.Run();

// record是C#的一个关键字，可以定义一个不可变的数据类型
internal record WeatherForecast(DateOnly Date, int TemperatureC, string? Summary)
{
    public int TemperatureF => 32 + (int)(TemperatureC / 0.5556);
}

record可以用于快速定义一个类

// 两者等效
record EditTodoItemRequest(int Id, TodoItemDTO Dto, TodoDb Db);

class EditTodoItemRequest
{
    public int Id { get; set; }
    public TodoItemDTO Dto { get; set; } = default!;
    public TodoDb Db { get; set; } = default!;
}

添加一个新Get

app.MapGet("/open/{path}", (string path) =>
{
    try
    {
        Process.Start("explorer.exe", path);
    }
    catch (Exception ex)
    {
        Console.WriteLine($"Can't open folder: {ex.Message}");
    }
});

http://localhost:xxxx/open/C%3A%5CUsers%5C28240%5Ccode

用文件浏览器打开本地的C:\Users\28240\code路径

解析Request内容

app.MapGet("/do", (HttpRequest request) =>
{
    var prop_a = request.Query["a"];
    var prop_b = request.Query["b"];
    var sessionid = request.Query["sessionid"];    
});

http://localhost:xxxx/do?a=hello&b=world&sessionid=default

输入一个文件

app.MapPost("/do", (HttpRequest request) =>
{
    var sourceFile = request.Form.Files[0];
    // 将 http 请求的文件保存在本地
    using (var st = new FileStream(localPath, FileMode.Create))
    {
        sourceFile.CopyTo(st); 
    }
    ...
});

返回一个文件

app.MapPost("/download", (HttpRequest request) =>
{
    return Results.File(System.IO.File.OpenRead(localVideoPath), "video/mp4");
});

用python下载这个文件

response = requests.post(url, headers=headers, files={"file": file})
if response.status_code == 200:
    print("Request successful!")
    with open('received_file.mp4', 'wb') as f:
        f.write(response.content)
    print("文件已保存为 'received_file.mp4'")
else:
    print("Request failed with status code:", response.status_code)

url转义规则

除了下面这些保留字外，用%{两位十六进制}进行转义

字符	转义形式
空格	%20
!	%21
*	%2A
’	%27
(	%28
)	%29
;	%3B
:	%3A
@	%40
&	%26
=	%3D
+	%2B
$	%24
,	%2C
/	%2F
?	%3F
#	%23
[	%5B
]	%5D

Web Socket

除了简单的Web API，我们有时也会用到Web Socket

服务端代码

// Program.cs
var builder = WebApplication.CreateBuilder(args);

builder.Services.AddControllers();

var app = builder.Build();

var webSocketOptions = new WebSocketOptions
{
    KeepAliveInterval = TimeSpan.FromMinutes(2)
};

app.UseWebSockets(webSocketOptions);

app.MapControllers();

app.Run();

namespace SocketDemo.Controllers
{
    public class xxxxController : ControllerBase
    {
        [Route("/ws")]
        public async Task Get()
        {
            if (HttpContext.WebSockets.IsWebSocketRequest)
            {
                using var webSocket = await HttpContext.WebSockets.AcceptWebSocketAsync();
                await Echo(webSocket);
            }
            else
            {
                HttpContext.Response.StatusCode = StatusCodes.Status400BadRequest;
            }
        }

        private static async Task Echo(WebSocket webSocket)
        {
            Console.WriteLine("First Connect");
            var buffer = new byte[1024 * 4];
            var receiveResult = await webSocket.ReceiveAsync(
                new ArraySegment<byte>(buffer), CancellationToken.None);

            while (!receiveResult.CloseStatus.HasValue)
            {
                var segment = new ArraySegment<byte>(buffer, 0, receiveResult.Count);
                await webSocket.SendAsync(
                    segment,
                    receiveResult.MessageType,
                    receiveResult.EndOfMessage,
                    CancellationToken.None);
                Console.WriteLine($"Send: {Encoding.UTF8.GetString(segment.Array, segment.Offset, segment.Count)}");

                receiveResult = await webSocket.ReceiveAsync(
                    new ArraySegment<byte>(buffer), CancellationToken.None);
            }

            await webSocket.CloseAsync(
                receiveResult.CloseStatus.Value,
                receiveResult.CloseStatusDescription,
                CancellationToken.None);
        }
    }
}

客户端代码

import asyncio
import websockets

async def connect_to_server():
    uri = "wss://localhost:7167/ws"  # 替换成你的服务器地址

    async with websockets.connect(uri) as websocket:
        print(f"Connected to {uri}")

        try:
            while True:
                message = input("Enter message to send (or 'exit' to quit): ")

                if message.lower() == "exit":
                    break

                await websocket.send(message)
                print(f"> Sent: {message}")

                response = await websocket.recv()
                print(f"< Received: {response}")

        finally:
            await websocket.close()
            print("WebSocket connection closed")

asyncio.run(connect_to_server())

注：客户端连接websocket时，不使用http、https，而是ws、wss