这段时间抽空学习了一下强大的网络库libevent，其使用标准C语言编写，支持Windows、Linux、Mac等等主流操作系统，早期版本不支持Windows的IOCP，最新版本已经添加上了，在网上找了一下资料，发现使用IOCP的libevent示例太少，于是结合网上的资料，自己整理编写了一下libevent使用IOCP的小例子。该示例同时支持IPV4以及IPV6的连接。
#ifdef __cplusplus
extern "C"
{
#endif //包含所需要的头文件
#include "event2/event.h"
#include "event2/listener.h"
#include "event2/bufferevent.h"
#include "event2/thread.h"
#include "event2/buffer.h" #ifdef __cplusplus
};
#endif #ifdef _MSC_VER
#pragma comment(lib,"ws2_32.lib")
#pragma comment(lib,"libevent_core.lib")
#endif //监听回调函数
void listener_cb(evconnlistener *listener, evutil_socket_t fd,
struct sockaddr *sock, int socklen, void *arg); //从Socket接收消息的回调函数
void socket_read_cb(bufferevent *bev, void *arg); //从Socket事件的回调函数
void socket_event_cb(bufferevent *bev, short events, void *arg); int main()
{
WORD wVersionRequested;
WSADATA wsaData;
int err; /* Use the MAKEWORD(lowbyte, highbyte) macro declared in Windef.h */
wVersionRequested = MAKEWORD(2, 2);
//这里必须初始化网络，不然会创建Socket失败
err = WSAStartup(wVersionRequested, &wsaData);
if (err != 0) {
/* Tell the user that we could not find a usable */
/* Winsock DLL. */
printf("WSAStartup failed with error: %d\n", err);
return 1;
} struct sockaddr_in sin;
memset(&sin, 0, sizeof(struct sockaddr_in));
sin.sin_family = AF_INET;
sin.sin_port = htons(2000); struct sockaddr_in6 sin6;
memset(&sin6, 0, sizeof(struct sockaddr_in6));
sin6.sin6_family = AF_INET6;
sin6.sin6_port = htons(2000); //告诉libEvent使用Windows线程
//这句是必须的，不然会导致event_base_dispatch时一直处于Sleep状态，无法正常工作
evthread_use_windows_threads(); struct event_config* cfg = event_config_new();
event_config_set_flag(cfg,EVENT_BASE_FLAG_STARTUP_IOCP);
//根据CPU实际数量配置libEvent的CPU数
SYSTEM_INFO si;
GetSystemInfo(&si);
event_config_set_num_cpus_hint(cfg,si.dwNumberOfProcessors); event_base *base;
base = event_base_new_with_config(cfg);
event_config_free(cfg); // 绑定并监听IPV4端口
evconnlistener *listener = evconnlistener_new_bind(base, listener_cb, base,
LEV_OPT_REUSEABLE|LEV_OPT_CLOSE_ON_FREE,
10, (struct sockaddr*)&sin,
sizeof(sin)); // 绑定并监听IPV6端口
evconnlistener *listener6 = evconnlistener_new_bind(base, listener_cb, base,
LEV_OPT_REUSEABLE|LEV_OPT_CLOSE_ON_FREE,
10, (struct sockaddr*)&sin6,
sizeof(sin6)); //事件分发处理
event_base_dispatch(base); evconnlistener_free(listener);
evconnlistener_free(listener6);
event_base_free(base);
WSACleanup(); return 0;
} //一个新客户端连接上服务器了
//当此函数被调用时，libevent已经帮我们accept了这个客户端。该客户端的
//文件描述符为fd
void listener_cb(evconnlistener *listener, evutil_socket_t fd,
struct sockaddr *sock, int socklen, void *arg)
{
char Buffer[256];
sockaddr_in* addr = (sockaddr_in*)sock;
evutil_inet_ntop(addr->sin_family,&addr->sin_addr,Buffer,sizeof(Buffer));
printf("accept a client %d,IP:%s\n", fd,Buffer); event_base *base = (event_base*)arg; //为这个客户端分配一个bufferevent
bufferevent *bev = bufferevent_socket_new(base, fd,
BEV_OPT_CLOSE_ON_FREE | BEV_OPT_THREADSAFE); bufferevent_setcb(bev, socket_read_cb, NULL, socket_event_cb, NULL);
bufferevent_enable(bev, EV_READ | EV_PERSIST);
} void socket_read_cb(bufferevent *bev, void *arg)
{
char msg[4096]; size_t len;
// 这里一行一行的读取
char* p = evbuffer_readln(bufferevent_get_input(bev),&len,EVBUFFER_EOL_ANY);
if(p)
{
// 如果输入exit或者quit则退出程序
// 可以使用event_base_loopexit或者event_base_loopbreak
// 它们的区别是前者会把事件处理完才退出，后者是立即退出
if(!strcmp(p,"exit"))
event_base_loopexit(bufferevent_get_base(bev),NULL);
else if (!strcmp(p,"quit"))
event_base_loopbreak(bufferevent_get_base(bev)); printf("recv data:%s\n", p); int n = sprintf_s(msg,"srv recv data:%s\n",p);
//发送消息给客户端
bufferevent_write(bev, msg, n ); // 这里记得把分配的内存释放掉，不然会内存泄漏
free(p);
}
} void socket_event_cb(bufferevent *bev, short events, void *arg)
{
if (events & BEV_EVENT_EOF)
printf("connection closed\n");
else if (events & BEV_EVENT_ERROR)
printf("some other error\n"); //这将自动close套接字和free读写缓冲区
bufferevent_free(bev);
}