HttpFromTcp

An HTTP/1.1 server built from raw TCP sockets in C#, loosely following ThePrimeagen's boot.dev course for Go. Only I did it in C#.

(Why? Because I wanted to.)

Prerequisites

• .NET 10 SDK

Building

dotnet build HttpFromTcp.slnx

Running

dotnet run --project HttpFromTcp

The server listens on 127.0.0.1:42069. Pass --debug (or -d) for verbose output:

dotnet run --project HttpFromTcp -- --debug

Send a request with curl:

curl http://localhost:42069/

Testing

# Run all tests
dotnet test HttpFromTcp.slnx

# Run a single test project
dotnet test HttpFromTcp.Tests/HttpFromTcp.Tests.csproj
dotnet test ErrorsTests/ErrorsTests.csproj

# Run a single test by name
dotnet test HttpFromTcp.Tests/HttpFromTcp.Tests.csproj --filter RequestReader_GoodLine_Succeeds

Project Structure

Project	Description
HttpFromTcp	The server. Accepts TCP connections and parses HTTP/1.1 requests using System.IO.Pipelines.
Errors	Standalone error library. Errors are tree-structured (Nil, Message, Tree) and composed with ErrorFuncs.Join().
HttpFromTcp.Tests	xUnit v3 tests for the HTTP parser, including fragmented-stream tests that simulate slow network reads.
ErrorsTests	xUnit v2 tests for the Errors library.

How It Works

The server reads raw bytes from a TCP socket and incrementally parses HTTP/1.1 requests — no HttpListener, no ASP.NET, no Kestrel.

RequestReader uses a PipeReader and SequenceReader<byte> to parse request lines, headers, and bodies as data arrives. A state machine (Initialized → ReadingHeaders → ReadingBody → Done) drives the parsing so that incomplete reads simply wait for more data rather than failing.