What is cshttp?

cshttp is a small, fast, zero-dependency web server for C#, written in pure C# 7.3, that you embed in your own program.

It ships as a single DLL (~105 KB) that runs unchanged on .NET Framework 4.8 and .NET 8 / 9 / 10+. You don't need IIS, the ASP.NET Core runtime or any NuGet packages. Reference the DLL (or drop in the source files), call WebApp.Run, and your program is a web server.

using cshttp;

static class Program
{
    static void Main() => WebApp.Run(8080, OnRequest);

    static void OnRequest()
    {
        switch (Request.Path.ToLower())
        {
            case "/":
                Response.Write("<h1>Hello from cshttp!</h1>");
                break;
            default:
                Response.StatusCode = 404;
                Response.Write("404 Not Found");
                break;
        }
    }
}

Run it, open http://localhost:8080/, and the site is live.

The idea in one sentence

cshttp gives C# the classic, synchronous Request / Response programming model from ASP.NET System.Web, inside a self-contained .exe, built on top of a strict and secure HTTP/1.1 engine.

Why it exists

C# developers who wanted to serve HTTP have usually had to pick one of these:

• A whole framework: ASP.NET on IIS, or ASP.NET Core with Kestrel, dependency injection, middleware and async everywhere.
• HttpListener, which is tied to Windows http.sys.
• A hand-written parser, which tends to break on chunked bodies or multipart uploads and is open to request smuggling.

cshttp is a fourth option. Like llhttp in C, httparse in Rust or net/http in Go, it's a compact HTTP stack whose layers are explicit and can be used separately. Its handler code is plain, synchronous C#: a switch on the path, read Request.Form, call Response.Write.

What's inside: three layers in one DLL

┌───────────────────────────────────────────────────────────┐
│                  Your C# application code                 │
│          (a switch router + synchronous handlers)         │
└─────────────────────────────┬─────────────────────────────┘
┌─────────────────────────────▼─────────────────────────────┐
│ Server/  cshttp.server: the standalone server             │
│   TCP/TLS listener, keep-alive, timeouts, graceful stop   │
├───────────────────────────────────────────────────────────┤
│ Web/     cshttp.web: the Request/Response toolkit         │
│   HttpContext, QueryString, Form, Files, Cookies,         │
│   StaticFiles, MapPath, HttpUtility                       │
├───────────────────────────────────────────────────────────┤
│ Core/    cshttp.core: the HTTP/1.1 wire engine            │
│   byte-level parser, chunked decoder, response writer     │
└───────────────────────────────────────────────────────────┘

All three layers share one namespace, cshttp. Each layer depends only on the layers below it, so you can use just the part you need.

Deep dives: Tier 1: Core · Tier 2: Web · Tier 3: Server · Structure Overview

What writing an app looks like

If you've used classic ASP.NET, you already know the API:

cshttp follows System.Web's names and shapes but doesn't copy all of it. Web Forms, Session, HTTP modules and built-in authentication are out of scope.

How fast is it?

In the project's stress test (Intel i7-4770S, 4 cores, with 1,500 idle keep-alive connections plus 50 active clients), cshttp.server handled about 62,000 requests/sec on .NET 10 and 50,000 requests/sec on .NET Framework 4.8, with a p99 latency of about 6 ms. The 1,500 idle connections added only one OS thread. See the Benchmark Report.

Where cshttp fits

Good fit:

• Self-contained web apps and REST APIs shipped as a single .exe or Windows/Linux service
• Embedded admin UIs or dashboards inside desktop apps, services, games and tools
• Porting simple ASP.NET System.Web handlers off IIS
• Learning web development from first principles (see the 14-day tutorial on Tutorial)
• Behind Nginx in production: Nginx handles TLS and static files, cshttp handles dynamic routes

Not what it is:

• Not an MVC/Razor framework, DI container or middleware pipeline
• Not HTTP/2 or HTTP/3. cshttp speaks HTTP/1.1, and a reverse proxy like Nginx can serve HTTP/2 to clients.

Getting it

1. Starter pack: download cshttp-starter-pack.zip from Releases, unzip and run.
2. DLL reference: add cshttp.dll to your project.
3. Source inclusion: copy the Core/, Web/ and Server/ folders into your solution.

License

Public domain (The Unlicense). Free for any commercial or non-commercial use.