ent_set_timeouts(bev, struct timeval *READ, struct timeval *WRITE)来设置读写超时, 在error_cb里面处理超时。
*. read_cb和write_cb的原型是
void read_or_write_callback(struct bufferevent *bev, void *arg)
error_cb的原型是
void error_cb(struct bufferevent *bev, short error, void *arg) //这个是event的标准回调函数原型
可以从bev中用libevent的API提取出event_base、sockfd、input/output等相关数据，详情RTFM~
于是代码简化到只需要几行的read_cb和error_cb函数即可：
void
read_cb(
struct
bufferevent *bev,
void
*arg) {
char
line[256];
int
n;
evutil_socket_t fd = bufferevent_getfd(bev);
while
(n = bufferevent_read(bev, line, 256), n > 0)
bufferevent_write(bev, line, n);
}
void
error_cb(
struct
bufferevent *bev,
short
event,
void
*arg) {
bufferevent_free(bev);
}
于是一个支持大并发量的echo server就成型了！下面附上无注释的echo server源码，110行，多抄几遍，就能完全弄懂啦！更复杂的例子参见官方文档里面的【Example: A simpler ROT13 server with Libevent】
include
<stdio.h>
#
include
<stdlib.h>
#
include
<errno.h>
#
include
<assert.h>
#
include
<event2/event.h>
#
include
<event2/bufferevent.h>
#
define
LISTEN_PORT 9999
#
define
LISTEN_BACKLOG 32
void
do_accept(evutil_socket_t listener,
short
event,
void
*arg);
void
read_cb(
struct
bufferevent *bev,
void
*arg);
void
error_cb(
struct
bufferevent *bev,
short
event,
void
*arg);
void
write_cb(
struct
bufferevent *bev,
void
*arg);
int
main(
int
argc,
char
*argv[])
{
int
ret;
evutil_socket_t listener;
listener = socket(AF_INET, SOCK_STREAM, 0);
assert(listener > 0);
evutil_make_listen_socket_reuseable(listener);
struct
sockaddr_in sin;
sin.sin_family = AF_INET;
sin.sin_addr.s_addr = 0;
sin.sin_port = htons(LISTEN_PORT);
if
(bind(listener, (
struct
sockaddr *)&sin,
sizeof(sin)) < 0) {
perror("bind");
return
1;
}
if
(listen(listener, LISTEN_BACKLOG) < 0) {
perror("listen");
return
1;
}
printf
("Listening...\n");
evutil_make_socket_nonblocking(listener);
struct
event_base *base = event_base_new();
assert(base !=
NULL);
struct
event *listen_event;
listen_event = event_new(base, listener, EV_READ|EV_PERSIST, do_accept, (
void*)base);
event_add(listen_event,
NULL);
event_base_dispatch(base);
printf("The End.");
return
0;
}
void
do_accept(evutil_socket_t listener,
short
event,
void
*arg)
{
struct
event_base *base = (
struct
event_base *)arg;
evutil_socket_t fd;
struct
sockaddr_in sin;
socklen_t slen;
fd = accept(listener, (
struct
sockaddr *)&sin, &slen);
if
(fd < 0) {
perror("accept");
return;
}
if
(fd > FD_SETSIZE) {
perror("fd > FD_SETSIZE\n");
return;
}
printf("ACCEPT: fd = %u\n", fd);
struct
bufferevent *bev = bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE);
bufferevent_setcb(bev, read_cb,
NULL, error_cb, arg);
bufferevent_enable(bev, EV_READ|EV_WRITE|EV_PERSIST);
}
void
read_cb(
struct
bufferevent *bev,
void
*arg)
{
#
define
MAX_LINE 256
char
line[MAX_LINE+1];
int
n;
evutil_socket_t fd = bufferevent_getfd(bev);
while
(n = bufferevent_read(bev, line, MAX_LINE), n > 0) {
line[n] = '\0';
printf("fd=%u, read line: %s\n", fd, line);
bufferevent_write(bev, line, n);
}
}
void
write_cb(
struct
bufferevent *bev,
void
*arg) {}
void
error_cb(
struct
bufferevent *bev,
short
event,
void
*arg)
{
evutil_socket_t fd = bufferevent_getfd(bev);
printf("fd = %u, ", fd);
if
(event & BEV_EVENT_TIMEOUT) {
printf("Timed out\n"); //
if
bufferevent_set_timeouts() called
}
else
if
(event & BEV_EVENT_EOF) {
printf("connection closed\n");
}
else
if
(event & BEV_EVENT_ERROR) {
printf("some other error\n");
}
bufferevent_free(bev);
}
