Libevent事件的创建-scoke服务的创建-特征的获取和配置

Libevent 简介

Libevent是一款事件驱动的网络开发包，由于采用C语言开发体积小巧，跨平台，速度极快。大量开源项目使用了Libevent比如谷歌的浏览器和分布式的高速缓存系统memcached。libevent支持kqueue,select,poll,epoll,iocp。内部事件机制完全独立于公开事件API，libevent支持跨平台可以在Linux，*BSD，MacOSX,Solaris,Windows等平台上编译。

学习条件：具有一定的C/C++基础，熟悉Linux

环境搭建

• 配置zlib库

# 1. 解压zlib 1.2.11
tar xvf zlib-1.2.11.tar.gz
# 2. 编译
cd zlib-1.2.11/
./configure
make
make install

• 配置openssl库

# 1. 解压openssl-1.1.1.tar.gz
tar xvf openssl-1.1.1.tar.gz
# 2. 编译
cd openssl-1.1.1/
./configure
make
make install

• 配置libevent环境

# 1.加压liebevent 2.1.8
unzip libevent-master.zip
# 2. 编译
cd libevent-master/
./autogen.sh
./configure
make
make install
# 3.将动态路来连接到 /usr/lib 下或者执行以下  ldconfig
sudo ln -s /usr/local/lib/libevent-2.2.so.1 /usr/lib/libevent-2.2.so.1

实战实例

创建event_base

仅仅实现创建上下文

/***
 *  创建event base
 * */

#include 
#include 
using namespace std;
int main()
{

    std::cout << "test libevent!\n"; 
	//创建libevent的上下文
	event_base * base = event_base_new();
	if (base)
	{
		cout << "event_base_new success!" << endl;
	}
	return 0;
}

创建test_server

test_server中说明了如何使用libevent创建一个socket监听

evconnlistener_new_bind一个接口完成了socket的创建，绑定和监听。

/***
 *  创建event base
 * */

#include 
#include 
#include 
#include 
#include 
#include "event_interface.h"

using namespace std;

/**
   A callback that we invoke when a listener has a new connection.

   @param listener The evconnlistener
   @param fd The new file descriptor
   @param addr The source address of the connection
   @param socklen The length of addr
   @param user_arg the pointer passed to evconnlistener_new()
 */
void listen_cb(struct evconnlistener * evConnListener, evutil_socket_t evUtilSockFd, struct sockaddr * sockAddr, int socklen, void *data)
{
	cout << "listen cb is called" << endl;
}

int main(int argc, char *argv[])
{
    //1. 忽略管道信号,发送数据给已关闭的socket
	//一些socket程序莫名宕掉的原因
	if(signal(SIGPIPE, SIG_IGN) == SIG_ERR)
	{
		cout << "ignal pipe signal" << endl;
	}

    std::cout << "test libevent!\n"; 
	//创建libevent的上下文
	event_base * base = event_base_new();
	if (!base)
	{
		cout << "event_base_new failed." << endl;
		return -1;
	}
	else
	{
		cout << "event_base_new success!" << endl;
	}

	//监听端口
	//socket, bind, listen
	sockaddr_in sockIn;
	memset(&sockIn, 0, sizeof(sockIn));
	sockIn.sin_family = AF_INET;
	sockIn.sin_port = htons(SERVER_PORT);
	/* 地址没有指定因为对sockIn进行了了memset，地址赋值为0代表着可以为任意可以用的地址 */

	struct evconnlistener *pEvListener = evconnlistener_new_bind(base, /* libevent的上下文 */
				listen_cb, /* 接收到连接的回调 */
				base, /* 回调函数参数 */
				LEV_OPT_REUSEABLE|LEV_OPT_CLOSE_ON_FREE, /* 地址重用，evconnlistenner关闭同时关闭socket */
				10, /* 连接队列的大小，对应的listen函数 */
				(sockaddr *)&sockIn,   /* 绑定地址和端口 */
				sizeof(sockIn)
				);

	//事件分发处理
	if(base)
		event_base_dispatch(base);
	
	if(pEvListener)
		evconnlistener_free(pEvListener);

	if(base)
	event_base_free(base);
	return 0;
}

创建test_conf

test_conf主要是实现了，测试当前系统中支持的方法类型和事件特征的支持情况。

support methods 
epoll
poll
select

EV_FEATURE_ET events are supported.
EV_FEATURE_O1 events are supported.
EV_FEATURE_FDS events are not supports.
EV_FEATURE_EARLY_CLOSE events are supported.
event base new with config sucess

#include 
#include 
#include 
#include 
#include 
#include 
#include "event_interface.h"

using namespace std;

int main()
{
	//忽略管道信号，发送数据给已关闭的socket
	if (signal(SIGPIPE, SIG_IGN) == SIG_ERR)
		return 1;

	//创建配置上下文
	event_config *config = event_config_new();
	//显示支持的网络模式
	const char **methods = 	event_get_supported_methods();
	cout << "support methods " << endl;
	for(int i = 0; methods[i] != NULL; i++)
	{
		cout << methods[i] << endl;
	}
	//设置特征，确认特征时候生效
	//这个features在linux中设置没有效果，因为linux中本来就是支持ET模式的，边缘触发模式
	// 设置了EV_FEATURE_FDS其他特征嗯就无法设置
	//也就是所支持了EV_FEATURE_FDS  其他的特征都是无法支持的
	int ret = 
	event_config_require_features(config, EV_FEATURE_ET|EV_FEATURE_EARLY_CLOSE);
	if(OK != ret)
	{
		cerr << "event config require features failed." << endl;
		return ERROR; 
	}
	//初始化libevent上下文
	event_base *base =  event_base_new_with_config(config);

	//config一旦配置好就不需要在使用了
	event_config_free(config);

	if(!base)
	{
		cerr << "event base new with config failed!" << endl;
		//首次失败就创建一个base取默认值，若是再次失败就返回失败
		base = event_base_new();
		if(!base)
		{
			cerr << "event base new failed." << endl;	
			return ERROR;
		}
	}
	else
	{
		//确认特征那些生效
		int f = event_base_get_features(base);
		if(f&EV_FEATURE_ET)
		{
			cout << "EV_FEATURE_ET events are supported." << endl;
		}
		else
		{
			cout << "EV_FEATURE_ET events are not supports." << endl;
		}

		if(f&EV_FEATURE_O1)
		{
			cout << "EV_FEATURE_O1 events are supported." << endl;
		}
		else
		{
			cout << "EV_FEATURE_O1 events are not supports." << endl;
		}

		if(f&EV_FEATURE_FDS)
		{
			cout << "EV_FEATURE_FDS events are supported." << endl;
		}
		else
		{
			cout << "EV_FEATURE_FDS events are not supports." << endl;
		}

		if(f&EV_FEATURE_EARLY_CLOSE)
		{
			cout << "EV_FEATURE_EARLY_CLOSE events are supported." << endl;
		}
		else
		{
			cout << "EV_FEATURE_EARLY_CLOSE events are not supports." << endl;
		}
		cout << "event base new with config sucess" << endl;
		event_base_free(base);
	}

	return 0;
}