libevent 封装了低层最高效的网络模型,windows的compIO,linux下的epoll模型,freebsd的kqueue,提供统一的异步调用接口; 以事件方式驱动,chrome,memcached 都在使用该框架.

      libevent 同时也支持DNS,HTTP协议和RPC调用框架

 

一. 定时器



#include <stdio.h>
#include <event.h>

void onTime(int sock,short event,void *arg)
{
  printf("Game over!\n");

  struct timeval tv;
  tv.tv_sec = 1;
  tv.tv_usec = 0;

  // 事件执行后,默认就被删除,需要重新add,使之重复执行
  event_add((struct event*)arg,&tv);
}

int main()
{
  // 初始化事件
  event_init();

  // 设置定时器回调函数
  struct event evTime;
  evtimer_set(&evTime,onTime,&evTime);

  struct timeval tv;  // 1s后执行
  tv.tv_sec = 1;
  tv.tv_usec = 0;
  
        // 添加事件
  event_add(&evTime,&tv);
  // 循环派发事件
  event_dispatch();

  return 0;
}



    编译: gcc -o  time_test time_test.c -I/usr/local/libevent/include -L/usr/local/libevent/lib -levent

 

二. TCP服务器

    

#include <stdio.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <event.h>


struct event_base *base;

// 读事件
void onRead(int clifd,short ievent,void *arg)
{
  int ilen;
  char buf[1500];

  ilen = recv(clifd,buf,1500,0);

  if(ilen <= 0)
  {
    printf("Client close\n");
    
    struct event *pread = (struct event*)arg;
    event_del(pread);
    delete pread;

    close(clifd);
    return;
  }
  
  buf[ilen] = '\0';
  printf("Accpet: %s\n",buf);
}

// 连接事件
void onAccept(int svrfd,short ievent,void *arg)
{
  int clifd;
  struct sockaddr_in cliaddr;

  socklen_t sinsize = sizeof(cliaddr);
  clifd = accept(svrfd,(struct sockaddr*)&cliaddr,&sinsize);

  struct event *pread = new event;
  event_set(pread,clifd,EV_READ|EV_PERSIST,onRead,pread);  // 注册读(写)事件
  event_base_set(base,pread);
  event_add(pread,NULL);
}


int main()
{
  int svrfd;
  struct sockaddr_in svraddr;

  memset(&svrfd,0,sizeof(svraddr));
  svraddr.sin_family = AF_INET;
  svraddr.sin_port = htons(1234);
  svraddr.sin_addr.s_addr = inet_addr("127.0.0.1");

  svrfd = socket(AF_INET,SOCK_STREAM,0);
  bind(svrfd,(struct sockaddr*)&svraddr,sizeof(svraddr));

  listen(svrfd,10);

  // 初始化事件库
  base = event_base_new();

  // 初始化一个连接事件,EV_PRESIST指定重复执行该事件
  struct event evlisten;
  event_set(&evlisten,svrfd,EV_READ|EV_PERSIST,onAccept,NULL);

  // 设置为base事件
  event_base_set(base,&evlisten);
  // 添加事件
  event_add(&evlisten,NULL);
  // 事件循环
  event_base_dispatch(base);

  return 0;

}

    要实现windows下更高效的IOCP方式的API,IOCP在准备好读写事件时不会通知你的程序去拷贝数据,而时在数据完成从内核态拷贝到用户态时才通知应用程序. libevent 2提供了 bufferevent 接口,支持这种编程范式 

 

三. HTTP服务器

   



#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <event.h>
#include <evhttp.h>

void reqHandler(struct evhttp_request *req,void *arg)
{
  struct evbuffer *buf = evbuffer_new();
  
  // 发送响应
  evbuffer_add_printf(buf, "Thanks for the request");
  evhttp_send_reply(req,HTTP_OK,"Client",buf);
  
  evbuffer_free(buf);
  
  return;
}

int main(int argc,char **argv)
{
  short port = 8000;
  const char *addr = "192.168.1.11";
  struct evhttp *httpserv = NULL;

  event_init();
        // 启动http服务
  httpserv = evhttp_start(addr,port);

  // 设置回调
  evhttp_set_gencb(httpserv, reqHandler,NULL);
  printf("Server started on port %d\n",port);

  event_dispatch();

  return 0;
}



    浏览器访问: ​​http://192.168.1.11:8000​​ 会显示 Thanks for the request