enet.c

ENet - Simple, lightweight and reliable UDP networking library written on pure C

_{Brought to you by @lsalzman, @inlife, @zaklaus, @nxrighthere and other contributors}

Disclaimer

This is a fork of the original library lsalzman/enet. While original repo offers a stable, time-tested wonderful library, we are trying to change some things, things, which can't be reflected on the main repo, like:

• integrated ipv6 support
• added monotonic time
• applied project-wide code style change
• cleaned up project
• single-header style code
• removed some of older/outdated methods
• and many other various changes

Description

ENet's purpose is to provide a relatively thin, simple and robust network communication layer on top of UDP (User Datagram Protocol). The primary feature it provides is optional reliable, in-order delivery of packets, and fragmentation.

ENet omits certain higher level networking features such as authentication, lobbying, server discovery, encryption, or other similar tasks that are particularly application specific so that the library remains flexible, portable, and easily embeddable.

Installation

Download file releases/latest/enet.h and just add to your project.

Usage (Shared library)

Build the shared library:

$ cmake -B build -DENET_SHARED=1 -DCMAKE_BUILD_TYPE=Release
$ cmake --build build

Use it:

#define ENET_DLL
#include <enet.h>
#include <stdio.h>

int main() {
    if (enet_initialize () != 0) {
        printf("An error occurred while initializing ENet.\n");
        return 1;
    }

    enet_deinitialize();
    return 0;
}

Usage (Static library)

Build the static library:

$ cmake -B build -DENET_STATIC=1 -DCMAKE_BUILD_TYPE=Release
$ cmake --build build

Use it:

#include <enet.h>
#include <stdio.h>

int main() {
    if (enet_initialize () != 0) {
        printf("An error occurred while initializing ENet.\n");
        return 1;
    }

    enet_deinitialize();
    return 0;
}

Usage (Single Header, Preferred)

In this case, library will be embedded to the project itself.

Make sure you add a define for ENET_IMPLEMENTATION exactly in one source file before including the enet.h.

Here is a simple server and client demo, it will wait 1 second for events, and then exit if none were found:

Server:

#define ENET_IMPLEMENTATION
#include <enet.h>
#include <stdio.h>

int main() {
    if (enet_initialize () != 0) {
        printf("An error occurred while initializing ENet.\n");
        return 1;
    }

    ENetAddress address = {0};

    address.host = ENET_HOST_ANY; /* Bind the server to the default localhost.     */
    address.port = 7777; /* Bind the server to port 7777. */

    #define MAX_CLIENTS 32

    /* create a server */
    ENetHost * server = enet_host_create(&address, MAX_CLIENTS, 2, 0, 0);

    if (server == NULL) {
        printf("An error occurred while trying to create an ENet server host.\n");
        return 1;
    }

    printf("Started a server...\n");

    ENetEvent event;

    /* Wait up to 1000 milliseconds for an event. (WARNING: blocking) */
    while (enet_host_service(server, &event, 1000) > 0) {
        switch (event.type) {
            case ENET_EVENT_TYPE_CONNECT:
                printf("A new client connected from %x:%u.\n",  event.peer->address.host, event.peer->address.port);
                /* Store any relevant client information here. */
                event.peer->data = "Client information";
                break;

            case ENET_EVENT_TYPE_RECEIVE:
                printf("A packet of length %lu containing %s was received from %s on channel %u.\n",
                        event.packet->dataLength,
                        event.packet->data,
                        event.peer->data,
                        event.channelID);
                /* Clean up the packet now that we're done using it. */
                enet_packet_destroy (event.packet);
                break;

            case ENET_EVENT_TYPE_DISCONNECT:
                printf("%s disconnected.\n", event.peer->data);
                /* Reset the peer's client information. */
                event.peer->data = NULL;
                break;

            case ENET_EVENT_TYPE_DISCONNECT_TIMEOUT:
                printf("%s disconnected due to timeout.\n", event.peer->data);
                /* Reset the peer's client information. */
                event.peer->data = NULL;
                break;

            case ENET_EVENT_TYPE_NONE:
                break;
        }
    }

    enet_host_destroy(server);
    enet_deinitialize();
    return 0;
}

Client:

#include <stdio.h>
#define ENET_IMPLEMENTATION
#include "enet.h"

int main() {
  if (enet_initialize() != 0) {
    fprintf(stderr, "An error occurred while initializing ENet.\n");
    return EXIT_FAILURE;
  }

  ENetHost* client = { 0 };
  client = enet_host_create(NULL /* create a client host */,
    1 /* only allow 1 outgoing connection */,
    2 /* allow up 2 channels to be used, 0 and 1 */,
    0 /* assume any amount of incoming bandwidth */,
    0 /* assume any amount of outgoing bandwidth */);
  if (client == NULL) {
    fprintf(stderr,
      "An error occurred while trying to create an ENet client host.\n");
    exit(EXIT_FAILURE);
  }

  ENetAddress address = { 0 };
  ENetEvent event = { 0 };
  ENetPeer* peer = { 0 };
  /* Connect to some.server.net:1234. */
  enet_address_set_host(&address, "127.0.0.1");
  address.port = 7777;
  /* Initiate the connection, allocating the two channels 0 and 1. */
  peer = enet_host_connect(client, &address, 2, 0);
  if (peer == NULL) {
    fprintf(stderr,
      "No available peers for initiating an ENet connection.\n");
    exit(EXIT_FAILURE);
  }
  /* Wait up to 5 seconds for the connection attempt to succeed. */
  if (enet_host_service(client, &event, 5000) > 0 &&
    event.type == ENET_EVENT_TYPE_CONNECT) {
    puts("Connection to some.server.net:1234 succeeded.");
  } else {
    /* Either the 5 seconds are up or a disconnect event was */
    /* received. Reset the peer in the event the 5 seconds   */
    /* had run out without any significant event.            */
    enet_peer_reset(peer);
    puts("Connection to some.server.net:1234 failed.");
  }

  // Receive some events
  enet_host_service(client, &event, 5000);

  // Disconnect
  enet_peer_disconnect(peer, 0);

  uint8_t disconnected = false;
  /* Allow up to 3 seconds for the disconnect to succeed
   * and drop any packets received packets.
   */
  while (enet_host_service(client, &event, 3000) > 0) {
      switch (event.type) {
      case ENET_EVENT_TYPE_RECEIVE:
          enet_packet_destroy(event.packet);
          break;
      case ENET_EVENT_TYPE_DISCONNECT:
          puts("Disconnection succeeded.");
          disconnected = true;
          break;
      }
  }

  // Drop connection, since disconnection didn't successed
  if (!disconnected) {
      enet_peer_reset(peer);
  }

  enet_host_destroy(client);
  enet_deinitialize();
}

Tutorials

More information, examples and tutorials can be found at the official site: http://enet.bespin.org/