vvvlan / facil.io

Your powerful network backend in C, with HTTP and Websocket support

facil.io - a mini-framework for C web applications

facil.io is a C mini-framework for web applications and includes:

• A fast HTTP/1.1 and Websocket static file + application server.
• Support for custom network protocols for both server and client connections.
• A pub/sub process cluster engine for Websocket pub/sub.
• Optional connectivity with Redis.
• Optional dynamic types designed with web applications in mind (Strings, Hashes, Arrays etc').
• JSON parsing and formatting for easy network communication.

facil.io powers the HTTP/Websockets Ruby Iodine server and it can easily power your application as well.

facil.io provides high performance TCP/IP network services to Linux / BSD (and macOS) by using an evented design (as well as thread pool and forking support) and provides an easy solution to the C10K problem.

You can read more about facil.io on the facil.io website.

#include "http.h" /* the HTTP facil.io extension */
// We'll use this callback in `http_listen`, to handles HTTP requests
void on_request(http_request_s* request);
// Listen to HTTP requests and start facil.io
int main(int argc, char const **argv) {
  // listen on port 3000 and any available network binding (NULL == 0.0.0.0)
  http_listen(3000, NULL, .on_request = on_request );
  // start the server
  facil_run(.threads = 1);
}
// Easy HTTP handling
void on_request(http_request_s* request) {
  http_response_s * response = http_response_create(request);
  http_response_log_start(response);
  http_response_set_cookie(response, .name = "my_cookie", .value = "data");
  http_response_write_header(response, .name = "X-Data", .value = "my data");
  http_response_write_body(response, "Hello World!\r\n", 14);
  http_response_finish(response);
}

Using facil.io in your project

It's possible to either start a new project with facil.io or simply add it to an existing one. GNU make is the default build system and CMake is also supported. Notice that facil.io is requires some C11 support from the compiler.

Starting a new project with facil.io

To start a new project using the facil.io framework, run the following command in the terminal (change appname to whatever you want):

 $ bash <(curl -s https://raw.githubusercontent.com/boazsegev/facil.io/master/scripts/new/app) appname

You can review the script here. In short, it will create a new folder, download a copy of the stable branch, add some demo boiler plate code and run make clean (which is required to build the tmp folder structure).

Next, edit the makefile to remove any generic features you don't need, such as the DUMP_LIB feature, the DEBUG flag or the DISAMS disassembler and start development.

Credit to @benjcal for suggesting the script.

Notice: The master branch is the development branch. Please select the latest release tag for the latest stable release version.

Adding facil.io to an existing project

facil.io is a source code library, so it's possible to simply copy the source code into an existing project and start using the library right away.

To use the library in an existing project, clone the git repo and run:

 $ make libdump

This will dump all the library files into a folder called libdump. The header files are in libdump/include and the source files are in libdump/src. The folder libdump/all contains all the source and header files mixed together.

Copy the header and source files to the appropriate location in your project and start using the library.

Using facil.io as a CMake submodule

facil.io also supports both git and CMake submodules. Credit to @OwenDelahoy (PR#8).

First, add the repository as a submudule using git:

git submodule add https://github.com/boazsegev/facil.io.git

Then add the following line the project's CMakeLists.txt

add_subdirectory(facil.io)

More Examples

Writing HTTP and Websocket services in C is easy with facil.io.

Websockets

facil.io really shines when it comes to Websockets and real-time applications, where the kqueue/epoll engine gives the framework a high performance running start.

Here's a full-fledge example of a Websocket echo server, a Websocket broadcast server and an HTTP "Hello World" (with an optional static file service) all rolled into one:

#include "websockets.h" // includes the "http.h" header

#include <stdio.h>
#include <stdlib.h>

/* ******************************
The Websocket echo implementation
*/

void ws_open(ws_s * ws) {
  fprintf(stderr, "Opened a new websocket connection (%p)\n", (void * )ws);
}

void ws_echo(ws_s * ws, char * data, size_t size, uint8_t is_text) {
  // echos the data to the current websocket
  websocket_write(ws, data, size, is_text);
}

void ws_shutdown(ws_s * ws) { websocket_write(ws, "Shutting Down", 13, 1); }

void ws_close(ws_s * ws) {
  fprintf(stderr, "Closed websocket connection (%p)\n", (void * )ws);
}

/* ********************
The HTTP implementation
*/

void on_request(http_request_s * request) {
  http_response_s * response = http_response_create(request);
  http_response_log_start(response); // logging
  // websocket upgrade.
  if (request->upgrade) {
    websocket_upgrade(.request = request, .on_message = ws_echo,
                      .on_open = ws_open, .on_close = ws_close, .timeout = 40,
                      .on_shutdown = ws_shutdown, .response = response);
    return;
  }
  // HTTP response
  http_response_write_body(response, "Hello World!", 12);
  http_response_finish(response);
}

/****************
The main function
*/

#define THREAD_COUNT 1
int main(void) {
  // easily support a command line interface
  fio_cli_start(argc, argv, NULL);
  fio_cli_accept_num("port p", "the port to listen to, defaults to 3000.");
  fio_cli_accept_bool("log v", "enable logging");
  fio_cli_accept_num("public-folder, www",
                     "enables a static file service from the folder's root.");
  const char * port = fio_cli_get_str("port");
  if (!port) // make sure NULL resolves to a default port.
    port = "3000";    
  http_listen("3000", NULL,  .on_request = on_request,
                             .public_folder = fio_cli_get_str("www"),
                             .log_static = fio_cli_get_int("v"));
  facil_run(.threads = THREAD_COUNT);
  fio_cli_end(); // clean up CLI data
  return 0;
}

A Custom Protocol (an Echo example)

facil.io's API is designed for both simplicity and an object oriented approach, using network protocol objects and structs to avoid bloating function arguments and to provide sensible default behavior.

Here's a simple Echo example (test with telnet to port "3000").

#include "facil.h" // the core library header

// Performed whenever there's pending incoming data on the socket
static void perform_echo(intptr_t uuid, protocol_s * prt) {
  (void)prt;
  char buffer[1024] = {'E', 'c', 'h', 'o', ':', ' '};
  ssize_t len;
  while ((len = sock_read(uuid, buffer + 6, 1018)) > 0) {
    sock_write(uuid, buffer, len + 6);
    if ((buffer[6] | 32) == 'b' && (buffer[7] | 32) == 'y' &&
        (buffer[8] | 32) == 'e') {
      sock_write(uuid, "Goodbye.\n", 9);
      sock_close(uuid); // closes after `write` had completed.
      return;
    }
  }
}
// performed whenever "timeout" is reached.
static void echo_ping(intptr_t uuid, protocol_s * prt) {
  (void)prt;
  sock_write(uuid, "Server: Are you there?\n", 23);
}
// performed during server shutdown, before closing the socket.
static void echo_on_shutdown(intptr_t uuid, protocol_s *prt) {
  (void)prt;
  sock_write(uuid, "Echo server shutting down\nGoodbye.\n", 35);
}
// performed after the socket was closed and the currently running task had
// completed.
static void destroy_echo_protocol(intptr_t old_uuid, protocol_s * echo_proto) {
  if (echo_proto) // always error check, even if it isn't needed.
    free(echo_proto);
  fprintf(stderr, "Freed Echo protocol at %p\n", (void * )echo_proto);
  (void)old_uuid;
}
// performed whenever a new connection is accepted.
static inline protocol_s * create_echo_protocol(intptr_t uuid, void * arg) {
  // create a protocol object
  protocol_s * echo_proto = malloc(sizeof( * echo_proto));
  // set the callbacks
  * echo_proto = (protocol_s){
      .service = "echo",
      .on_data = perform_echo,
      .on_shutdown = echo_on_shutdown,
      .ping = echo_ping,
      .on_close = destroy_echo_protocol,
  };
  // write data to the socket and set timeout
  sock_write(uuid, "Echo Service: Welcome. Say \"bye\" to disconnect.\n", 48);
  facil_set_timeout(uuid, 10);
  // print log
  fprintf(stderr, "New Echo connection %p for socket UUID %p\n",
          (void * )echo_proto, (void * )uuid);
  // return the protocol object to attach it to the socket.
  return echo_proto;
  (void)arg; // we don't use this
}
// creates and runs the server
int main(void) {
  // listens on port 3000 for echo services.
  facil_listen(.port = "3000", .on_open = create_echo_protocol);
  // starts and runs the server
  facil_run(.threads = 10);
  return 0;
}

---

Forking, Contributing and all that Jazz

Sure, why not. If you can add Solaris or Windows support to evio, that could mean facil would become available for use on these platforms as well (as well as the HTTP protocol implementation and all the niceties).

If you encounter any issues, open an issue (or, even better, a pull request with a fix) - that would be great :-)

Hit me up if you want to:

• Help me write HPACK / HTTP2 protocol support.

• Help me design / write a generic HTTP routing helper library for the http_request_s struct.

• If you want to help me write a new SSL/TLS library or have an SSL/TLS solution we can fit into facil (as source code).

• If you want to help promote the library, that would be great as well. Perhaps publish benchmarks) or share your story.

• Writing documentation into the facil.io website would be great. I keep the source code documentation fairly updated, but sometimes I can be a lazy bastard.