Implement an HTTP/1.1 Server That Serves a File

Request Format

HTTP/1.1 rides on TCP port 80 (or 443 with TLS). A typical request looks like:

c
Loading…

The blank line after headers marks the end of the header block. POST/PUT requests add a body after that line.

Response Format

The server replies with a status line and headers:

c
Loading…

Key headers for a file server:

Host: required for virtual hosting
Content-Length: exact body size in bytes
Connection: keep-alive or close

A minimal server reads the request line with recv(), splits method, URI, and version, maps /index.html to a filesystem path, and writes the status line plus headers before streaming the file body. No framework handles framing for you at this level.

Why This Exercise

This task asks you to parse the request line, map the URI to a file, and construct a response with raw sockets. nginx does this same byte-level parsing on port 80 and 443, and mismatched Content-Length handling between a server and an upstream proxy is the root cause of real HTTP request-smuggling CVEs. RFC 9112 governs every header and status line you construct in this exercise.

Write a C program that implements a simple HTTP/1.1 server. The server should parse incoming requests and serve a static file or a directory listing.

Requirements:

Create a TCP socket, bind to a port (e.g., 8080), and listen for connections
Accept a client connection and read the HTTP request
Parse the request line to extract the method (GET) and URI
Construct an HTTP/1.1 response status line
If the URI maps to an existing file, read it and send a 200 OK response
Include Content-Length and Content-Type headers
If the file is not found, send a 404 Not Found response
Show the raw HTTP response construction with printf
Do not use any external HTTP libraries

Request Format

HTTP/1.1 rides on TCP port 80 (or 443 with TLS). A typical request looks like:

c
Loading…

The blank line after headers marks the end of the header block. POST/PUT requests add a body after that line.

Response Format

The server replies with a status line and headers:

c
Loading…

Key headers for a file server:

Host: required for virtual hosting
Content-Length: exact body size in bytes
Connection: keep-alive or close

Why This Exercise

Write a C program that implements a simple HTTP/1.1 server. The server should parse incoming requests and serve a static file or a directory listing.

Requirements:

Create a TCP socket, bind to a port (e.g., 8080), and listen for connections
Accept a client connection and read the HTTP request
Parse the request line to extract the method (GET) and URI
Construct an HTTP/1.1 response status line
If the URI maps to an existing file, read it and send a 200 OK response
Include Content-Length and Content-Type headers
If the file is not found, send a 404 Not Found response
Show the raw HTTP response construction with printf
Do not use any external HTTP libraries

Topic Overview

Request Format

Response Format

Why This Exercise

Implementation Task

Progressive Hints

Resources

Open Source

Implement an HTTP/1.1 Server That Serves a File

Topic Overview

Request Format

Response Format

Why This Exercise

Implementation Task

Progressive Hints

Resources

Open Source