🧵 Multi-threaded HTTP Server (Sockets + Thread Pool)

A from-scratch HTTP/1.1 server built using Python sockets and threading.
It supports persistent connections, secure path handling, static HTML rendering, binary file streaming, and JSON POST uploads — all using a bounded thread pool for concurrency.

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📘 Overview

This server implements core HTTP/1.1 semantics, including:

• Host validation
• Connection persistence (Keep-Alive)
• RFC 7231-compliant Date headers (GMT)
• Static file serving
• Binary streaming with Content-Disposition
• JSON upload handling

It serves resources from the resources/ directory and supports both GET and POST requests.

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📂 Project Structure

project/
├─ server.py
└─ resources/
   ├─ index.html
   ├─ about.html
   ├─ contact.html
   ├─ sample.txt
   ├─ notes.txt
   ├─ sample.json
   ├─ bad.json
   ├─ logo.png
   ├─ banner.png
   ├─ photo.jpg
   ├─ gallery.jpg
   └─ uploads/

• server.py — main multi-threaded TCP HTTP server
• resources/ — static assets and upload directory for POST /upload

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⚙️ Build & Run

Requirements

• Python 3.10+
• Uses only standard libraries: socket, threading, queue, os, json, etc.

Default Run

python3 server.py

➡️ Binds to 127.0.0.1:8080 with thread pool size 10.

Custom Run

python3 server.py 8000 0.0.0.0 20

➡️ Runs on port 8000, host 0.0.0.0, and pool size 20.

• Accept backlog: 50 pending connections.

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🧩 Features

🔹 HTTP Parsing

• Supports GET and POST
• Parses:
  • Method, path, version, headers, body
• Max request size: 8192 bytes
• Invalid requests → 400 Bad Request

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🔹 GET Handling

File Type	Content-Type	Behavior
.html	text/html; charset=utf-8	Rendered inline
.txt, .png, .jpg, .jpeg	application/octet-stream	Downloaded as attachments

• Binary files are streamed in 8KB chunks for efficiency.

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🔹 POST /upload

• Only accepts: Content-Type: application/json
• Non-JSON → 415 Unsupported Media Type
• Valid JSON is saved in:

  resources/uploads/upload_YYYYMMDD_HHMMSS_xxxx.json
  

• Response: 201 Created with file path.

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🔄 Connection Management

Protocol	Default Behavior
HTTP/1.1	Persistent unless Connection: close
HTTP/1.0	Closed unless Connection: keep-alive

• Includes header:

  Keep-Alive: timeout=30, max=100
  

• Server enforces:
  • 30s idle timeout
  • 100 requests per connection

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📜 Logging

Logs include:

• Startup info
• Request details
• Host validation results
• File transfer sizes
• Status codes
• Thread pool usage and saturation warnings
• Worker activity snapshots

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📦 Binary Transfer

• Uses:

  Content-Type: application/octet-stream
  Content-Disposition: attachment; filename="..."
  

• Ensures consistent file download behavior.
• Uses sendall() with 8KB chunked streaming for large files.

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🧵 Thread Pool Architecture

• Fixed-size pool of daemon worker threads.
• Threads fetch sockets from a Queue.
• Each thread handles multiple requests (Keep-Alive).
• If all workers are busy:
  • New connections are queued.
  • Logs: Thread pool saturation warning.

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🔐 Security

• Host validation:
  Only allows:

  localhost:PORT
  127.0.0.1:PORT
  <configured_host>:PORT
  

  Missing or mismatched Host → 400 / 403.

• Path traversal protection:

  • Rejects .., ./, and absolute paths.
  • Ensures access only within resources/.

• All responses include:

  Date: <RFC 7231 HTTP-date in GMT>
  

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🧪 Testing

Prepare the resources/ folder with the listed files.

HTML Rendering

curl -i http://127.0.0.1:8080/
curl -i http://127.0.0.1:8080/about.html

Binary Downloads

curl -i -O -J http://127.0.0.1:8080/logo.png
curl -i -O -J http://127.0.0.1:8080/photo.jpg
curl -i -O -J http://127.0.0.1:8080/sample.txt

JSON Uploads

curl -i -H "Content-Type: application/json" -d '{"ok":true}' http://127.0.0.1:8080/upload

Error Cases

Case	Expected
Missing file	404 Not Found
Unsupported method	405 Method Not Allowed
Non-JSON POST	415 Unsupported Media Type
Missing Host header	400 Bad Request
Host mismatch / traversal	403 Forbidden

Keep-Alive

curl -i --http1.1 -H "Connection: keep-alive" http://127.0.0.1:8080/

Concurrency Test

printf "%s\n" logo.png photo.jpg sample.txt | xargs -I{} -P 5 curl -O -J http://127.0.0.1:8080/{}

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⚠️ Known Limitations

• Request body limit: 8192 bytes
• Chunked transfer-encoding not implemented
• MIME mapping limited to .html, .txt, .png, .jpg, .jpeg
• No TLS/HTTPS (local use only)
• Single-process design for simplicity

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🧠 Educational Purpose

This project demonstrates:

• Manual socket-level HTTP handling
• Thread pool design and synchronization
• File I/O and safe path canonicalization
• Basic concurrency debugging and performance observation

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✨ Author

Built with 💚 by Prince Shakya