cHTTP

cHTTP is an HTTP client and server library for C with minimal dependencies and distributed as a single chttp.c file.

Here is a list of features:

• HTTP 1.1 client and server
• Fully non-blocking
• Cross-Platform (Windows & Linux)
• HTTPS support (using OpenSSL)
• Virtual Hosts
• Single-threaded
• Zero-copy interface

Getting Started

The library is distributed in a single amalgamated chttp.c file or as a static library, so you can:

1. Download chttp.c and chttp.h from the repository (no need to clone the project)

2. or clone the project and build the static library my running

make libchttp.a

If you used the amalgamated files, these are the flags required to build a project with cHTTP:

# Linux
gcc your_app.c chttp.c

# Windows
gcc your_app.c chttp.c -lws2_32

If you are using the static library, instead of adding chttp.c, you will need to add the -lchttp flag.

By default, the library is built without HTTPS. To enable it, add the flags -DHTTPS_ENABLED -lssl -lcrypto.

# Linux + HTTPS
gcc your_app.c chttp.c -DHTTPS_ENABLED -lssl -lcrypto

# Windows + HTTPS
gcc your_app.c chttp.c -lws2_32 -DHTTPS_ENABLED -lssl -lcrypto

Example

Here is a client performing a GET request:

#include <stdio.h>
#include <chttp.h>

int main(void)
{
    http_global_init();

    HTTP_String url = HTTP_STR("http://example.com/index.html");

    HTTP_String headers[] = {
        HTTP_STR("User-Agent: cHTTP"),
    };

    HTTP_Response *res = http_get(url, headers, 1);

    fwrite(res->body.ptr, 1, res->body.len, stdout);

    http_response_free(res);
    http_global_free();
    return 0;
}

And this is a server:

#include <chttp.h>

int main(void)
{
    http_global_init();
    HTTP_Server *server = http_server_init(HTTP_STR("127.0.0.1"), 8080);

    for (;;) {

        HTTP_Request *req;
        HTTP_ResponseBuilder builder;
        http_server_wait(server, &req, &builder);

        http_response_builder_status(builder, 200);
        http_response_builder_header(builder, "Content-Type: text/plain");
        http_response_builder_body(builder, HTTP_STR("Hello, world!"));
        http_response_builder_done(builder);
    }

    http_server_free(server);
    http_global_free();
    return 0;
}

Platform Support

cHTTP officially supports Linux and Windows.

HTTPS support

Currently, HTTPS is implemented using OpenSSL which comes preinstalled on Linux but not Windows. It must be enabled by passing the -DHTTPS_ENABLED flag to gcc when building your program:

Scalability

cHTTP is designed to reach moderate scale to allow a compact and easy to work with implementation. The non-blocking I/O is based on poll() which I would say works up to about 500 concurrent connections. If you have more than that, you should consider APIs like epoll, io_uring, and I/O completion ports. If you do go that route, you can still reuse the cHTTP I/O independent core (see HTTP_Engine) to handle the HTTP protocol for you, both for client and server.