看到一个文章[Go] 不到 100 行代码实现一个支持 CONNECT 动词的 HTTP 服务器
在NET8中如何实现
创建项目为MiniApi

编辑Program.cs文件。

var builder = WebApplication.CreateSlimBuilder(args);

var app = builder.Build();

// 将HTTP请求通过协议升级机制转为远程TCP请求（WebSocket分支，Nginx支持） 
app.Map("/http2tcp", async (context) =>
{
    var upgradeFeature = context.Features.Get<Microsoft.AspNetCore.Http.Features.IHttpUpgradeFeature>();
    if (upgradeFeature != null && upgradeFeature.IsUpgradableRequest)
    {
        context.Features.Get<Microsoft.AspNetCore.Http.Timeouts.IHttpRequestTimeoutFeature>()?.DisableTimeout();
        context.Response.Headers.Connection = Microsoft.Net.Http.Headers.HeaderNames.Upgrade;
        context.Response.Headers.Upgrade = "http2tcp/1.0";
        Stream stream = await upgradeFeature.UpgradeAsync();

        using System.Net.Sockets.TcpClient tcpClient = new System.Net.Sockets.TcpClient();
        await tcpClient.ConnectAsync(System.Net.IPEndPoint.Parse("127.0.0.1:1000"));
        using System.Net.Sockets.NetworkStream network = tcpClient.GetStream();

        var taskX = network.CopyToAsync(stream);
        var tsakY = stream.CopyToAsync(network);
        Task.WaitAny(taskX, tsakY);
    }
});

// 将HTTP请求通过CONNECT方法转为TCP请求（CONNECT分支）主流浏览器都支持  https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods/CONNECT
app.MapMethods("", new[] { HttpMethods.Connect }, async (context) =>
{
    var auth = context.Request.Headers["Proxy-Authorization"];

    await context.Response.Body.FlushAsync();

    var socket = context.Features.Get<Microsoft.AspNetCore.Connections.Features.IConnectionSocketFeature>()!.Socket;
    var stream = new System.Net.Sockets.NetworkStream(socket);

    using var tcpClient = new System.Net.Sockets.TcpClient();
    await tcpClient.ConnectAsync(System.Net.IPEndPoint.Parse(context.Request.Host.Value));
    using var network = tcpClient.GetStream();

    var taskX = network.CopyToAsync(stream);
    var tsakY = stream.CopyToAsync(network);
    Task.WaitAny(taskX, tsakY);
    await socket.DisconnectAsync(true);
    socket.Close();
});

app.Run();

HTTP Upgrade 客户端请求方式

GET http://127.0.0.1:5199/http2tcp HTTP/1.1
Connection: upgrade
Upgrade: example/1, foo/2
User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; WOW64; Trident/7.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E)
Accept-Encoding: gzip, deflate
Host: 127.0.0.1:5199

HTTP CONNECT 客户端请求方式

CONNECT 127.0.0.1:1000 HTTP/1.1
Host: 127.0.0.1:1000
Proxy-Authorization: basic aGVsbG86d29ybGQ=

如下是数据传输示意图。