Static HTML Server

A lightweight, multi-threaded static file server built entirely from scratch in C# using raw TCP sockets.

Instead of relying on high-level HTTP abstractions (like ASP.NET Core or HttpListener), this project implements the fundamental networking and protocol parsing layers manually to understand how web servers actually communicate with modern browsers under the hood.

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🛠️ Architecture & Design

The project is structured around clean, decoupled domain interfaces to ensure a solid separation of concerns:

• StaticFileServer: The core infrastructure piece. It initializes a TcpListener, listens for incoming client connections on a background loop, parses raw incoming HTTP request text, and streams back byte-perfect HTTP/1.1 formatted responses.
• StaticFilePipeline: The coordinator. It orchestrates the lifecycle of a request by sanitizing paths, fetching files, determining MIME types, and packaging the result.
• IPathSanitizer: A critical security layer that maps request paths (like /index.html) to the local wwwroot directory while actively preventing directory traversal attacks.
• IFileProvider: Abstracted file system reader that reads physical files as raw byte streams asynchronously.
• IMimeTypeProvider: Maps file extensions (.html, .css, .js) to their official MIME standard types so browsers know how to render them.

Unit tests for this build are implemented using C# and xUnit.

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🧠 Key Takeaways & Lessons Learned

Building this server from the socket level up was an eye-opening exercise in system-level programming. Here are the core concepts I mastered while building and debugging this:

1. The HTTP/1.1 Protocol is Just Structured Text

Before this, HTTP felt like magic. Now I know that an HTTP response is literally just a plain-text header separated from a raw binary payload by a double line break (\r\n\r\n). Getting the socket to write the exact string structure (HTTP/1.1 200 OK, Content-Type, Content-Length) before dumping the raw file bytes was very insigthful.

2. Parameter Ordering Matters (Always Check Your Stack Traces)

During development, a swapped parameter in my path sanitizer (rawPath passed where rootDirectory was expected) taught me a valuable lesson in reading stack traces carefully. What looked like a complex directory error was just a simple argument mismatch. Debugging this sharpened my runtime diagnostics skills.

3. Asynchronous I/O and Socket Lifecycles

Handling TcpClient streams asynchronously using async/await showed me how modern servers handle concurrent connections without blocking. I also learned the hard way that if you don't explicitly flush your network stream and handle your using blocks correctly, the browser will hang on an ERR_EMPTY_RESPONSE because the connection dropped before the bytes could travel.

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🚀 How to Run It

Prerequisites

• .NET 10.0 SDK

Setup

1. Clone the repository:

   git clone [https://github.com/Zaido219/static-html-server.git](https://github.com/Zaido219/static-html-server.git)
   cd static-html-server

Add your website assets (HTML, CSS, JS, images) into the StaticHtmlServer/wwwroot directory.

2. Run the application:

   dotnet run --project StaticHtmlServer

3. Open your browser and navigate to: http://localhost:8080/index.html

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📝 Disclaimer

It would'nt be fair if I say that I did not use AI for this build, at the same time it would also not be fair if I say that i vibe-coded this entirely. I wrote and architected this myself, using Gemini mostly to help debug issues and clean up the code.