Multi-Threaded HTTP Proxy Server

A project for understanding socket programming in C and implementing a fully functional multi-threaded HTTP proxy server with request forwarding capabilities.

Overview

This project demonstrates advanced concepts of network programming in C, including multi-threaded socket handling, HTTP request parsing, proxy forwarding, and response handling. It's designed as an educational tool for learning TCP socket programming, multi-threading, HTTP protocol implementation, and proxy server architecture.

Project Structure

multi-threaded-proxy-server/
├── main.c              # Main program entry point
├── socket/
│   ├── socket.c        # Socket creation and multi-threading
│   ├── socket.h        # Socket function declarations
│   └── conn.c          # Client connection handling
├── proxy/
│   ├── proxy.c         # Proxy forwarding logic
│   └── proxy.h         # Proxy function declarations
├── utils/
│   ├── logger.c        # Logging functionality
│   ├── logger.h        # Logger declarations
│   ├── parser.c        # HTTP request parser
│   ├── parser.h        # Parser declarations
│   ├── helper.c        # Utility functions
│   └── helper.h        # Helper declarations
├── Makefile            # Build configuration
├── main                # Compiled executable
└── README.md           # This file

Currently Implemented

Core Socket Functionality

• Multi-threaded Server: Handles multiple client connections simultaneously
• Socket Creation & Binding: TCP socket creation with proper error handling
• Connection Acceptance: Accepts client connections with thread creation

HTTP Request Processing

• Dynamic Buffer Management: Handles requests larger than buffer size
• HTTP Request Parsing: Manual character-by-character parsing
• Header Extraction: Parses all HTTP headers into linked list structure
• Body Handling: Extracts request body when present
• Completion Detection: Detects complete HTTP requests with proper boundary checking

Proxy Forwarding

• URL Path Extraction: Converts full URLs to proper HTTP request paths
• Request Reconstruction: Rebuilds HTTP requests for target servers
• Target Server Connection: Establishes connections to target servers
• Response Forwarding: Forwards complete responses back to clients

Response Handling

• Chunked Transfer Encoding: Properly handles chunked responses
• Content-Length Support: Handles responses with Content-Length headers
• Complete Response Detection: Ensures full responses are received before forwarding

Memory Management

• Dynamic Memory Allocation: Proper buffer expansion for large requests
• Linked List Headers: Efficient storage of HTTP headers
• Memory Cleanup: Proper resource management

Building the Project

# Clean and build
make clean && make

# Run the proxy server
./main <port>

Usage

# Start the proxy server on port 8888
./main 8888

# Test with HTTP client (Postman, curl, etc.)
# Use localhost:8888 as the proxy server

Key Functions

initializeSocket(int port)

Creates, binds, and starts listening for connections with multi-threading support.

handleClient(int c_fd)

Handles individual client connections with dynamic buffer management and HTTP parsing.

parseRequest(char *buff, size_t tsize)

Manually parses HTTP requests, extracting method, path, headers, and body.

forwardRequest(struct parsed_request *req, char *req_buff, int req_buff_len, char *resp_buff, size_t *resp_len)

Forwards HTTP requests to target servers and receives responses.

receiveResponse(int tar_con_fd, char *resp_buff, size_t *resp_buff_len)

Receives complete HTTP responses from target servers, handling both chunked and Content-Length encoding.

Development Status

• Multi-threaded server implementation
• Dynamic buffer expansion
• HTTP request parsing (method, path, headers, body)
• Signal handling for graceful shutdown
• Memory management and cleanup
• Structured logging system
• Proxy forwarding logic
• Target server connection
• Response forwarding
• Chunked transfer encoding support
• URL path extraction and request reconstruction
• Complete response handling

Features

HTTP Protocol Support

• Methods: GET, POST, PUT, DELETE, etc.
• Headers: All standard HTTP headers
• Body: Request and response body handling
• Encoding: Chunked transfer encoding and Content-Length

Proxy Capabilities

• URL Parsing: Extracts paths from full URLs
• Request Forwarding: Reconstructs requests for target servers
• Response Handling: Forwards complete responses to clients
• Multi-threading: Handles multiple concurrent requests

Error Handling

• Connection Errors: Proper handling of connection failures
• Memory Errors: Graceful handling of allocation failures
• Protocol Errors: Robust HTTP parsing with error recovery

Learning Focus

This project helps understand:

Network Programming

• Socket programming fundamentals
• Multi-threading with pthread
• TCP connection lifecycle
• Signal handling
• Proxy server architecture

HTTP Protocol

• HTTP request structure
• Header parsing techniques
• Body handling
• Protocol completion detection
• Chunked transfer encoding
• URL parsing and reconstruction

Memory Management

• Dynamic memory allocation
• Buffer management
• Linked list implementation
• Resource cleanup

System Programming

• File descriptor management
• Thread synchronization
• Error handling
• Process signals

Testing

The proxy server can be tested with:

• Postman: Send HTTP requests to any target server
• curl: Command-line HTTP requests
• Web browsers: Configure proxy settings
• Custom HTTP clients

Example Test Scenarios

# Test with local server
curl -x localhost:8888 http://localhost:3000/

# Test with external server
curl -x localhost:8888 http://httpbin.org/get

# Test with Postman
# Set proxy to localhost:8888 and send requests to any URL

Enhancements can be made to the project

• Request/response caching
• Load balancing
• Request filtering
• Performance monitoring
• Logging
• Error handling
• Memory management
• Thread synchronization
• File descriptor management
• Process signals