tcp

A small set of Go utilities and examples demonstrating low-level HTTP-over-TCP parsing and serving.

This repository contains a simple HTTP server built on top of a custom request parser and response writer, plus small helper programs for listening to raw TCP and sending UDP messages.

ref: https://www.rfc-editor.org/rfc/rfc9112

Project layout

• cmd/httpserver — HTTP server binary (uses the internal server to accept connections and a handler that implements a few routes).
• cmd/tcplistener — raw TCP listener that accepts a single connection and prints parsed request parts.
• cmd/udpsender — simple UDP client that reads from stdin and sends lines to localhost:42069.
• internal/headers — header parsing utilities.
• internal/request — request parsing from a reader (supports parsing request-line, headers and Content-Length body).
• internal/response — response writer helpers (status line, headers, chunked bodies, trailers).
• internal/server — small server wrapper that accepts TCP connections, uses the request parser and response writer, and invokes a Handler.

Default listening port: 42069 (hard-coded in the examples).

Build & run

From the repository root you can build or run components directly with go run or go build.

Run the HTTP server:

go run ./cmd/httpserver

Or build the binary:

go build -o bin/httpserver ./cmd/httpserver
./bin/httpserver

Run the TCP listener (prints a single parsed request then exits):

go run ./cmd/tcplistener

Run the UDP sender (interactive; sends lines to localhost:42069):

go run ./cmd/udpsender

Examples

Fetch the root page:

curl -v http://localhost:42069/

Proxy to httpbin (example):

curl -v http://localhost:42069/httpbin/get

Notes and implementation details

• The project implements a custom, minimal HTTP/1.1 parser and writer for educational purposes. It understands request-lines, headers, and bodies with Content-Length; it also supports writing chunked responses and trailers.
• Header names are normalized to lowercase in internal/headers and validated for allowed characters.
• The server in internal/server uses the parser and writes the response buffer back to the connection after the handler returns.
• The module name is tcpgo per go.mod.

Development

• Run go build ./... to compile all packages and check for compile errors.
• Tests can be run with go test ./....