Multi-threaded C-HTTP Server

A high-performance HTTP/1.1 server built from the ground up in C. This project handles concurrent connections using threads and features a custom-built compression engine that implements LZ77 and Huffman Coding to mimic GZIP.

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Quick Start

1. Compile the Server

You will need gcc and the pthread library (standard on Linux/macOS):

gcc -o server main.c -lpthread

2. Run the Server

Specify the directory where you want to store or serve files:

./server --directory .

The server will start listening on port 4221.

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Manual Testing (Telnet)

You can test the raw HTTP interaction by using telnet. This allows you to see exactly how the server parses headers and sends responses.

Perform a GET Request

Connect to the server:

telnet localhost 4221

Then paste the following and press Enter twice:

GET /echo/hello_world HTTP/1.1
Host: localhost:4221

Perform a POST Request (File Upload)

Connect to the server:

telnet localhost 4221

Then paste the following and press Enter:

POST /files/note.txt HTTP/1.1
Host: localhost:4221
Content-Length: 13

Hello from C!

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API Endpoints

Endpoint	Method	Result
/	GET	Returns a simple 200 OK.
/echo/{str}	GET	Returns {str} in the response body.
/user-agent	GET	Returns the client's User-Agent string.
/files/{name}	GET	Downloads the specified file from the directory.
/files/{name}	POST	Saves the request body as a new file.

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Core Features

Multi-threading

The server uses pthread_create for every incoming connection. This ensures that a large file download from one user does not block smaller or faster requests from other clients.

Custom Compression Pipeline

If a request includes the Accept-Encoding: gzip header, the server passes the response data through two compression stages:

1. LZ77 A sliding window algorithm that replaces repeated substrings with distance/length pairs.

2. Huffman Coding A frequency-based encoding system using a Min-Heap to build a prefix tree for bit-level compression.

Persistent Connections

The server respects the Connection: close header. If it is not present, the server attempts to keep the socket open for subsequent requests until a 15-second timeout is reached.

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Requirements

• GCC compiler
• POSIX-compliant OS (Linux, Unix, or macOS)
• pthread library

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Created as a deep-dive into systems programming and network protocols.