10.1 Hello_World服务器(基于信号)

#include <string.h>
#include <errno.h>
#include <stdio.h>
#include <signal.h>
#ifndef WIN32
#include <netinet/in.h>
# ifdef _XOPEN_SOURCE_EXTENDED
#  include <arpa/inet.h>
# endif
#include <sys/socket.h>
#endif

#include <event2/bufferevent.h>
#include <event2/buffer.h>
#include <event2/listener.h>
#include <event2/util.h>
#include <event2/event.h>

static const char MESSAGE[] = "Hello, World!\n";

static const int PORT = 9995;

static void listener_cb(struct evconnlistener *, evutil_socket_t,
    struct sockaddr *, int socklen, void *);
static void conn_writecb(struct bufferevent *, void *);
static void conn_eventcb(struct bufferevent *, short, void *);
static void signal_cb(evutil_socket_t, short, void *);

int
main(int argc, char **argv)
{
        struct event_base *base;
        struct evconnlistener *listener;
        struct event *signal_event;

        struct sockaddr_in sin;
#ifdef WIN32
        WSADATA wsa_data;
        WSAStartup(0x0201, &wsa_data);
#endif

        base = event_base_new();
        if (!base) {
                fprintf(stderr, "Could not initialize libevent!\n");
                return 1;
        }

        memset(&sin, 0, sizeof(sin));
        sin.sin_family = AF_INET;
        sin.sin_port = htons(PORT);

        listener = evconnlistener_new_bind(base, listener_cb, (void *)base,
            LEV_OPT_REUSEABLE|LEV_OPT_CLOSE_ON_FREE, -1,
            (struct sockaddr*)&sin,
            sizeof(sin));

        if (!listener) {
                fprintf(stderr, "Could not create a listener!\n");
                return 1;
        }

        signal_event = evsignal_new(base, SIGINT, signal_cb, (void *)base);

        if (!signal_event || event_add(signal_event, NULL)<0) {
                fprintf(stderr, "Could not create/add a signal event!\n");
                return 1;
        }

        event_base_dispatch(base);

        evconnlistener_free(listener);
        event_free(signal_event);
        event_base_free(base);

        printf("done\n");
        return 0;
}

static void
listener_cb(struct evconnlistener *listener, evutil_socket_t fd,
    struct sockaddr *sa, int socklen, void *user_data)
{
        struct event_base *base = user_data;
        struct bufferevent *bev;

        bev = bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE);
        if (!bev) {
                fprintf(stderr, "Error constructing bufferevent!");
                event_base_loopbreak(base);
                return;
        }
        bufferevent_setcb(bev, NULL, conn_writecb, conn_eventcb, NULL);
        bufferevent_enable(bev, EV_WRITE);
        bufferevent_disable(bev, EV_READ);

        bufferevent_write(bev, MESSAGE, strlen(MESSAGE));
}

static void
conn_writecb(struct bufferevent *bev, void *user_data)
{
        struct evbuffer *output = bufferevent_get_output(bev);
        if (evbuffer_get_length(output) == 0) {
                printf("flushed answer\n");
                bufferevent_free(bev);
        }
}

static void
conn_eventcb(struct bufferevent *bev, short events, void *user_data)
{
        if (events & BEV_EVENT_EOF) {
                printf("Connection closed.\n");
        } else if (events & BEV_EVENT_ERROR) {
                printf("Got an error on the connection: %s\n",
                    strerror(errno));/*XXX win32*/
        }
        /* None of the other events can happen here, since we haven't enabled
         * timeouts */
        bufferevent_free(bev);
}

static void
signal_cb(evutil_socket_t sig, short events, void *user_data)
{
        struct event_base *base = user_data;
        struct timeval delay = { 2, 0 };

        printf("Caught an interrupt signal; exiting cleanly in two seconds.\n");

        event_base_loopexit(base, &delay);
}