a libevent example

libevent_example.c

/*
 ============================================================================
 Name        : libevent_sample.c
 Author      : killerg
 Version     :
 Copyright   : Your copyright notice
 Description : Hello World in C, Ansi-style
 ============================================================================
 */

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <errno.h>
#include <netinet/tcp.h>

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

struct client_ctx_st {
	struct event_base* base;
	int shutting;
};


int
set_linger(int fd, int onoff, int linger) {
	struct linger l = { .l_linger = linger, .l_onoff = onoff};
	int res = setsockopt(fd, SOL_SOCKET, SO_LINGER, &l, sizeof(l));
	assert(res == 0);
	return res;
}


int
set_keepalive(int fd, int keepalive, int cnt, int idle, int intvl) {
	int res = setsockopt(fd, SOL_SOCKET, SO_KEEPALIVE, &keepalive, sizeof(keepalive));
	assert(res == 0);

	res = setsockopt(fd, IPPROTO_TCP, TCP_KEEPCNT, &idle, sizeof(idle));
	assert(res == 0);

	res = setsockopt(fd, IPPROTO_TCP, TCP_KEEPIDLE, &idle, sizeof(idle));
	assert(res == 0);

	res = setsockopt(fd, IPPROTO_TCP, TCP_KEEPINTVL, &intvl, sizeof(intvl));
	assert(res == 0);

	return res;
}


void
read_cb(struct bufferevent *bev, void *ctx) {
	struct client_ctx_st* client_ctx = ctx;

	int fd = bufferevent_getfd(bev);
	struct evbuffer* input = bufferevent_get_input(bev);
	struct evbuffer* output = bufferevent_get_output(bev);
	char* line = evbuffer_readln(input, NULL, EVBUFFER_EOL_ANY);
	if (line) {
		if (strcmp(line, "quit") == 0) {
			if (evbuffer_get_length(output) > 0)
				client_ctx->shutting = 1;
			else
				shutdown(fd, SHUT_RD);
		} else if (strcmp(line, "abort") == 0) {
			shutdown(fd, SHUT_RD);
		}
		if (!client_ctx->shutting)
			evbuffer_add_printf(output, "%s\n", line);
		free(line);
	}
}

void
write_cb(struct bufferevent *bev, void *ctx) {
	struct client_ctx_st* client_ctx = ctx;

	int fd = bufferevent_getfd(bev);
	struct evbuffer* input = bufferevent_get_input(bev);
	struct evbuffer* output = bufferevent_get_output(bev);

	if (evbuffer_get_length(output) == 0 && client_ctx->shutting)
		shutdown(fd, SHUT_RD);
}

void
event_cb(struct bufferevent *bev, short what, void *ctx) {
	struct client_ctx_st* client_ctx = ctx;
	int needfree = 0;

	if (what & BEV_EVENT_READING) {
		if (what & BEV_EVENT_EOF || what & BEV_EVENT_TIMEOUT)
			needfree = 1;
	}

	if (what & BEV_EVENT_ERROR) {
		needfree = 1;
	}

	if (needfree) {
		int errcode = evutil_socket_geterror(bufferevent_getfd(bev));
		printf("errcode:%d\n", errcode);
		bufferevent_free(bev);
		free(client_ctx);
	}
}

void
listener_cb(
		struct evconnlistener* l,
		evutil_socket_t nfd,
		struct sockaddr *addr,
		int socklen,
		void *ctx)
{
	struct event_base* base = ctx;

	set_linger(nfd, 1, 0);
	set_keepalive(nfd, 1, 1, 5, 5);

	struct bufferevent* bev = bufferevent_socket_new(base, nfd, BEV_OPT_CLOSE_ON_FREE);
	assert(bev);

	struct client_ctx_st* client_ctx = malloc(sizeof(*ctx));
	client_ctx->base = base;
	client_ctx->shutting = 0;

	bufferevent_setcb(bev, read_cb, write_cb, event_cb, client_ctx);
	bufferevent_enable(bev, EV_READ|EV_WRITE|EV_ET);
}

int
main(void) {
	struct event_base* base = event_base_new();

	struct sockaddr saddr;
	int socklen = sizeof(saddr);

	int ret = evutil_parse_sockaddr_port("0.0.0.0:9876", &saddr, &socklen);
	assert(ret == 0);

	struct evconnlistener* lev = evconnlistener_new_bind(base,
													listener_cb,
													base,
													LEV_OPT_CLOSE_ON_FREE|LEV_OPT_REUSEABLE,
													100,
													&saddr,
													socklen);
	assert(lev);

	event_base_dispatch(base);

	evconnlistener_free(lev);

	event_base_free(base);
}