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。

  1#ifdef __cplusplus
  2extern "C"
  3{
  4#endif
  5
  6//包含所需要的头文件
  7#include "event2/event.h"
  8#include "event2/listener.h"
  9#include "event2/bufferevent.h"
 10#include "event2/thread.h"
 11#include "event2/buffer.h"
 12
 13#ifdef __cplusplus
 14};
 15#endif
 16
 17#ifdef _MSC_VER
 18#pragma comment(lib,"ws2_32.lib")
 19#pragma comment(lib,"libevent_core.lib")
 20#endif
 21
 22//监听回调函数
 23void listener_cb(evconnlistener *listener, evutil_socket_t fd,
 24 struct sockaddr *sock, int socklen, void *arg);  
 25
 26//从Socket接收消息的回调函数
 27void socket_read_cb(bufferevent *bev, void *arg);
 28
 29//从Socket事件的回调函数
 30void socket_event_cb(bufferevent *bev, short events, void *arg);  
 31
 32int main()
 33{  
 34	WORD wVersionRequested;
 35	WSADATA wsaData;
 36	int err;
 37
 38	/* Use the MAKEWORD(lowbyte, highbyte) macro declared in Windef.h */
 39	wVersionRequested = MAKEWORD(2, 2);
 40	//这里必须初始化网络，不然会创建Socket失败
 41	err = WSAStartup(wVersionRequested, &wsaData);
 42	if (err != 0) {
 43		/* Tell the user that we could not find a usable */
 44		/* Winsock DLL.                                  */
 45		printf("WSAStartup failed with error: %d\n", err);
 46		return 1;
 47	}
 48
 49	struct sockaddr_in sin;
 50	memset(&sin, 0, sizeof(struct sockaddr_in));
 51	sin.sin_family = AF_INET;
 52	sin.sin_port = htons(2000);
 53
 54    struct sockaddr_in6 sin6;
 55	memset(&sin6, 0, sizeof(struct sockaddr_in6));
 56	sin6.sin6_family = AF_INET6;
 57	sin6.sin6_port = htons(2000);
 58
 59	//告诉libEvent使用Windows线程
 60	//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
 61	evthread_use_windows_threads();
 62
 63	struct event_config* cfg = event_config_new();
 64	event_config_set_flag(cfg,EVENT_BASE_FLAG_STARTUP_IOCP);
 65	//根据CPU实际数量配置libEvent的CPU数
 66	SYSTEM_INFO si;
 67	GetSystemInfo(&si);
 68	event_config_set_num_cpus_hint(cfg,si.dwNumberOfProcessors);
 69
 70	event_base *base;
 71	base = event_base_new_with_config(cfg); 
 72	event_config_free(cfg);
 73
 74	// 绑定并监听IPV4端口
 75	evconnlistener *listener = evconnlistener_new_bind(base, listener_cb, base,  
 76		LEV_OPT_REUSEABLE|LEV_OPT_CLOSE_ON_FREE,  
 77		10, (struct sockaddr*)&sin,  
 78		sizeof(sin));
 79
 80	// 绑定并监听IPV6端口
 81	evconnlistener *listener6 = evconnlistener_new_bind(base, listener_cb, base,  
 82		LEV_OPT_REUSEABLE|LEV_OPT_CLOSE_ON_FREE,  
 83		10, (struct sockaddr*)&sin6,  
 84		sizeof(sin6));
 85
 86	//事件分发处理
 87	event_base_dispatch(base);  
 88
 89	evconnlistener_free(listener);
 90	evconnlistener_free(listener6);
 91	event_base_free(base);
 92	WSACleanup();
 93
 94	return 0;  
 95}
 96
 97//一个新客户端连接上服务器了  
 98//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
 99//文件描述符为fd
100void listener_cb(evconnlistener *listener, evutil_socket_t fd,  
101struct sockaddr *sock, int socklen, void *arg)  
102{  
103	char Buffer[256];
104	sockaddr_in* addr = (sockaddr_in*)sock;
105	evutil_inet_ntop(addr->sin_family,&addr->sin_addr,Buffer,sizeof(Buffer));
106	printf("accept a client %d,IP:%s\n", fd,Buffer);
107
108	event_base *base = (event_base*)arg;  
109
110	//为这个客户端分配一个bufferevent  
111	bufferevent *bev =  bufferevent_socket_new(base, fd,  
112		BEV_OPT_CLOSE_ON_FREE | BEV_OPT_THREADSAFE);  
113
114	bufferevent_setcb(bev, socket_read_cb, NULL, socket_event_cb, NULL);  
115	bufferevent_enable(bev, EV_READ | EV_PERSIST);  
116}
117
118void socket_read_cb(bufferevent *bev, void *arg)  
119{  
120	char msg[4096];
121
122	size_t len;
123	// 这里一行一行的读取
124	char* p = evbuffer_readln(bufferevent_get_input(bev),&len,EVBUFFER_EOL_ANY);
125	if(p)
126	{
127		// 如果输入exit或者quit则退出程序
128		// 可以使用event_base_loopexit或者event_base_loopbreak
129		// 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
130		if(!strcmp(p,"exit"))
131			event_base_loopexit(bufferevent_get_base(bev),NULL);
132		else if (!strcmp(p,"quit"))
133			event_base_loopbreak(bufferevent_get_base(bev));
134
135		printf("recv data:%s\n", p);  
136
137		int n = sprintf_s(msg,"srv recv data:%s\n",p);
138		//发送消息给客户端
139		bufferevent_write(bev, msg, n );
140
141		// 这里记得把分配的内存释放掉，不然会内存泄漏
142		free(p);
143	}
144}
145
146void socket_event_cb(bufferevent *bev, short events, void *arg)  
147{  
148	if (events & BEV_EVENT_EOF)  
149		printf("connection closed\n");  
150	else if (events & BEV_EVENT_ERROR)  
151		printf("some other error\n");  
152
153	//这将自动close套接字和free读写缓冲区  
154	bufferevent_free(bev);  
155}