CN-project-term5

HTTP Server | Socket Programming

A production-grade, educational HTTP/1.1 and HTTP/1.0 server implemented using only Python standard library modules (socket, threading, queue, os, sys, time, datetime, json, random, string, logging, mimetypes).

Features

• Thread pool with connection queue (default 10 workers; configurable)
• HTTP/1.1 keep-alive (timeout=30s, max=100 requests/connection) and HTTP/1.0 close-by-default
• GET static file serving from resources/
  • text/html; charset=utf-8 for .html
  • application/octet-stream download for .txt, .png, .jpg, .jpeg
  • Binary-safe handling with Content-Disposition for downloads
• POST JSON upload to /upload saving files to resources/uploads/
• Security: path traversal prevention, Host header validation
• Comprehensive logging (console + logs/server.log)

Working :

1. Server Initialization:
   The server is initialized with host, port, and max worker threads. Logging and required directories (logs, resources, resources/uploads) are created.

2. Socket Binding and Listening:
   A TCP socket is created and bound to the host and port. The server listens for incoming connections with a backlog limit.

3. Thread Pool:
   Worker threads are created and wait for tasks from a Queue that holds pending connections. This allows handling multiple clients at the same time (concurent processing).

4. Connection Handling:
   Each incoming client socket is added to the pending queue. A worker thread picks it up, reads the HTTP request, and decodes it. The server handles both GET and POST requests. After processing, the server sends a response and optionally keeps the connection alive depending on the Connection header.

5. Request Parsing:
   The HTTP request is split into request line, headers, and body. Invalid requests are responded with a 400 Bad Request error.

6. Statistics and Logging:
   The server keeps track of total requests, current clients, and busy workers. Logs are stored in logs/server.log and also printed to console.

7. Graceful Shutdown:
   Signals like Ctrl+C trigger a shutdown sequence. All sockets are closed and threads exit safely, printing server stats before exit.

Directory Layout

project/
├── server.py
├── resources/
│   ├── index.html
│   ├── sample.html
│   ├── test.txt
│   ├── test.json
│   ├── logo.png
│   ├── photo.jpg
│   ├── large_image.png
│   ├── large_photo.jpg
│   └── uploads/           # created automatically if missing
└── logs/
    └── server.log         # created automatically

Quick Start

python3 server.py                 # 127.0.0.1:8080, 10 threads
python3 server.py 8000            # custom port
python3 server.py 8000 0.0.0.0    # custom host
python3 server.py 8000 0.0.0.0 20 # custom host, port, max_threads

Then open http://localhost:8080/ in your browser.

If port is busy:

lsof -nP -iTCP:8080 -sTCP:LISTEN
kill -9 <PID>

Testing

Browser

• Visit / for the dashboard and links to test files
• Use the JSON upload form to POST to /upload

curl

# HTML
curl -H "Host: localhost:8080" http://localhost:8080/

# Binary downloads
curl -H "Host: localhost:8080" -O http://localhost:8080/resources/test.txt
curl -H "Host: localhost:8080" -O http://localhost:8080/resources/logo.png
curl -H "Host: localhost:8080" -O http://localhost:8080/resources/photo.jpg

# JSON upload
curl -i -X POST http://localhost:8080/upload \
  -H "Host: localhost:8080" \
  -H "Content-Type: application/json" \
  -d '{"name":"test","value":123}'

Expected on success: 201 Created with JSON body including filename and size.

HTTP Behaviour

• Default Keep-Alive for HTTP/1.1. Close by default for HTTP/1.0 unless Connection: keep-alive.
• Server sets Date (RFC 7231), Content-Type, Content-Length, Connection, and Keep-Alive (timeout=30, max=100) where applicable.
• Error codes: 400, 403, 404, 405, 415, 500, 503 (with Retry-After).

Security

• Path traversal protection: canonicalize paths; block .., //, absolute escapes; only allow /, /upload, and files under /resources/.
• Host header validation: only localhost:PORT, 127.0.0.1:PORT, or configured host:port.
• All violations logged to logs/server.log.

Thread Pool

• Fixed-size pool using threading + queue.Queue
• Accept loop enqueues connections; workers dequeue and serve
• Logs queueing/dequeueing and active usage

Known Limitations

• No TLS/HTTPS (HTTP only)
• No compression (gzip/deflate)
• No auth/rate limiting
• Large file sends are buffered by process (sufficient for course scope)

Troubleshooting

• Address in use: free port 8080 via lsof/kill
• 403 on /upload: ensure server is latest and running; request must use Content-Type: application/json
• UI error parsing: the web UI handles HTML error responses gracefully; check logs/server.log