用libevent写个简单的server/client

libevent是一个轻量级的事件触发库，可以很好地利用在网络通讯上面，用其进行大量的异步，延时，重发等场景。

下面是一个server的demo

#include include

void cb_func(evutil_socket_t fd, short what, void *arg)
{

        int  client_len;
        evutil_socket_t client_fd;

        struct sockaddr_in client_address;
        evutil_socket_t fd1 = *(evutil_socket_t *)arg;
        printf("Got an event on socket %d:%s%s%s%s \n\r",
            (int) fd,
            (what&EV_TIMEOUT) ? " timeout" : "",
            (what&EV_READ)    ? " read" : "",
            (what&EV_WRITE)   ? " write" : "",
            (what&EV_SIGNAL)  ? " signal" : "");
        client_fd=accept(fd1, (struct sockaddr *)&client_address, &client_len);
}

void main_loop(evutil_socket_t fd1)
{
        struct event *ev1, *ev2;
        struct timeval five_seconds = {,};
        struct event_base *base = event_base_new();

        /* The caller has already set up fd1, fd2 somehow, and make them nonblocking. */
    /* 初始化事件 */
        ev1 = event_new(base, fd1, EV_READ|EV_PERSIST, cb_func,&fd1);
       //EV_PERSIST选项相当于让event_add()持续有效

        /* 注册事件 */
        event_add(ev1, NULL);
        //event_add(ev1, &five_seconds);
        /* 循环监听 */
        event_base_dispatch(base);

}

int main()
{
    evutil_socket_t server_sockfd, client_sockfd;
    int server_len, client_len;
    struct sockaddr_in server_address;
    struct sockaddr_in client_address;

/*  Remove any old socket and create an unnamed socket for the server.  */

    server_sockfd = socket(AF_INET, SOCK_STREAM, );

/*  Name the socket.  */

    server_address.sin_family = AF_INET;
    server_address.sin_addr.s_addr = htonl(INADDR_ANY);
    server_address.sin_port = htons();
    server_len = sizeof(server_address);
    bind(server_sockfd, (struct sockaddr *)&server_address, server_len);

//  Create a connection queue and wait for clients.  

    listen(server_sockfd, );
    main_loop(server_sockfd);
}