Question

I am running gcc compiler on ubuntu i am using an example to learn how to make a socket connection with libev i have libev4 and libev-dev installed but and everything works fine except when i add struct ev_loop *loop = ev_default_loop(0); its throws an undefined reference error can anyone please tell what is wrong here is my code

#include <stdio.h>
#include <netinet/in.h>
#include <ev.h>

#define PORT_NO 3033
#define BUFFER_SIZE 1024

int total_clients = 0;  // Total number of connected clients

void accept_cb(struct ev_loop *loop, struct ev_io *watcher, int revents);
void read_cb(struct ev_loop *loop, struct ev_io *watcher, int revents);

int main() {
    struct ev_loop *loop = ev_default_loop(0); <--error-->
    int sd;
    struct sockaddr_in addr;
    int addr_len = sizeof(addr);
    struct ev_io w_accept;

    // Create server socket
    if ((sd = socket(PF_INET, SOCK_STREAM, 0)) < 0) {
        perror("socket error");
        return (-1);
    }

    bzero(&addr, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(PORT_NO);
    addr.sin_addr.s_addr = INADDR_ANY;

    // Bind socket to address
    if (bind(sd, (struct sockaddr*) &addr, sizeof(addr)) != 0) {
        perror("bind error");
    }

    // Start listing on the socket
    if (listen(sd, 2) < 0) {
        perror("listen error");
        return (-1);
    }

    // Initialize and start a watcher to accepts client requests
    ev_io_init(&w_accept, accept_cb, sd, EV_READ);
    ev_io_start(loop, &w_accept); <-- error -->

    // Start infinite loop
    while (1) {
        ev_loop(loop, 0);
    }

    return (0);
}

/* Accept client requests */
void accept_cb(struct ev_loop *loop, struct ev_io *watcher, int revents) {
    struct sockaddr_in client_addr;
    socklen_t client_len = sizeof(client_addr);
    int client_sd;
    struct ev_io *w_client = (struct ev_io*) malloc(sizeof(struct ev_io));

    if (EV_ERROR & revents) {
        perror("got invalid event");
        return;
    }

    // Accept client request
    client_sd = accept(watcher->fd, (struct sockaddr *) &client_addr,
                       &client_len);

    if (client_sd < 0) {
        perror("accept error");
        return;
    }

    total_clients++; // Increment total_clients count
    printf("Successfully connected with client.\n");
    printf("%d client(s) connected.\n", total_clients);

    // Initialize and start watcher to read client requests
    ev_io_init(w_client, read_cb, client_sd, EV_READ);
    ev_io_start(loop, w_client); <--error-->
}

/* Read client message */
void read_cb(struct ev_loop *loop, struct ev_io *watcher, int revents) {
    char buffer[BUFFER_SIZE];
    ssize_t read;

    if (EV_ERROR & revents) {
        perror("got invalid event");
        return;
    }

    // Receive message from client socket
    read = recv(watcher->fd, buffer, BUFFER_SIZE, 0);

    if (read < 0) {
        perror("read error");
        return;
    }

    if (read == 0) {
        // Stop and free watchet if client socket is closing
        ev_io_stop(loop, watcher); <--error-->
        free(watcher);
        perror("peer might closing");
        total_clients--; // Decrement total_clients count
        printf("%d client(s) connected.\n", total_clients);
        return;
    } else {
        printf("message:%s\n", buffer);
    }

    // Send message bach to the client
    send(watcher->fd, buffer, read, 0);
    bzero(buffer, read);
}

I am getting multiple error that i have marked can anyone please tell me what’s wrong i did a lot of search but didn’t found anything.

Answer 1

Nothing looks wrong with the code, but I suspect you aren’t likning with libev. Add -lev to your compiler line:

gcc -o ev_test ev_test.c -lev