cebsocket: a lightweight websocket library for C

Cebsocket is a lightweight websocket library for C.

Usage

Usage is easy and simple. You can look to examples/ directory. You can build examples with make command.

Simple WebSocket Server

Here is an example for creating simple WebSocket server.

void on_data(cebsocket_clients_t* client, char* data) {
    printf("WebSocket Message: %s\n", data);
    
    char answer[500];
    sprintf(answer, "Answer to client: %s", data);

    cebsocket_send(client, answer);

    sprintf(answer, "Answer to broadcast: %s", data);

    cebsocket_send_broadcast(client, answer);
}

void on_connected(cebsocket_clients_t* client) {
    printf("Client connected #%d\n", client->id);
}

void on_disconnected(cebsocket_clients_t* client) {
    printf("Client disconnected #%d\n", client->id);
}

int main() {
    printf("Starting WebSocket server..\n");

    cebsocket_t* ws = cebsocket_init(8080);

    ws->on_data = on_data;
    ws->on_connected = on_connected;
    ws->on_disconnected = on_disconnected;
    
    cebsocket_listen(ws);
    
    return 0;
}

What about HTTP?

Cebsocket is designed to only handle WebSocket requests as a HTTP server. You can use it with Apache's mod_proxy_ws_tunnel.

What about SSL?

Also you can use Apache's mod_proxy_ws_tunnel for SSL.

Build

Building is simple just do make.

make clean; make

You will see websocket.o. You can use it like:

gcc -o hello hello.c websocket.o
./hello

Events

Thread Safety

Event handler functions get called from client thread so you must be sure for they are thread-safe.

void on_connected(cebsocket_clients_t* client)

Called when a client connected.

void on_disconnected(cebsocket_clients_t* client)

Called when a client disconnected.

void on_message(cebsocket_clients_t* client, char* data)

Called when a message is arrived from client.

Functions

extern cebsocket_t* cebsocket_init(int port)

Creates WebSocket server instance.

extern void cebsocket_listen(cebsocket_t* ws)

Starts listening new connections.

extern void cebsocket_send(cebsocket_clients_t* client, char* message)

Sends message to client.

extern void cebsocket_send_broadcast(cebsocket_clients_t* client, char* message)

Sends message to boradcast of client.

extern void cebsocket_send_all(cebsocket_t* ws, char* message)

Sends message to all clients.

Iterating Clients

Since ws->clients is a linked-list, you can iterate it like the following example.

cebsocket_clients_t* _client = ws->clients;

while (_client) {
    cebsocket_send(_client, message);
    _client = _client->next;
}

Types

cebsocket_t

The WebSocket server instance.

typedef struct cebsocket {
    int port;
    char* host_address;
    char* bind_address;
    cebsocket_clients_t* clients;
    cebsocket_clients_t* current_client;
    void (*on_data)(cebsocket_clients_t*, char*);
    void (*on_connected)(cebsocket_clients_t*);
    void (*on_disconnected)(cebsocket_clients_t*);
} cebsocket_t;

cebsocket_clients_t

The WebSocket client instance. It is also a linked-list.

typedef struct cebsocket_clients {
    cebsocket_t* ws;
    int id;
    int socket;
    int server_socket;
    int address;
    char* ws_key;
    void* data;
    cebsocket_clients_t* prev;
    cebsocket_clients_t* next;
} cebsoket_clients_t;

License

MIT