本章将带你了解几个比较著名的开源事件处理库，epoll使用起来比较复杂，很多开源项目对epoll进行了封装，如libevent、libuv等，本章还会传授你如何提高开发网络异步IO服务器的效率。

7-1 比较有名的异步IO处理库的介绍

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上面写的应该是libevhtp。
libevhtp是基于libevent开发的。
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evconnlistener_new_bind
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7-2 libevent实现高性能服务器

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  1. wget -c https://github.com/libevent/libevent/releases/download/release-2.1.12-stable/libevent-2.1.12-stable.tar.gz --no-check-certificate
  2. tar -xf libevent-2.1.12-stable.tar.gz
  3. cd libevent-2.1.12-stable/
  4. ./configure --prefix=/usr/local/libevent
  5. make && sudo make install

添加环境变量 sudo vim ~/.bashrc

  1. export PKG_CONFIG_PATH=/usr/local/libevent/lib/pkgconfig:$PKG_CONFIG_PATH
  2. export LD_LIBRARY_PATH=/usr/local/libevent/lib:$LD_LIBRARY_PATH

source ~/.bashrc
查看打印
ubuntu@VM-8-4-ubuntu:~$ pkg-config —libs —cflags libevent
-I/usr/local/libevent/include -L/usr/local/libevent/lib -levent

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libevent_tcp_server.c

  1. #include <event2/listener.h>
  2. #include <event2/bufferevent.h>
  3. #include <event2/buffer.h>
  4. #include <event2/thread.h>
  6. #include <arpa/inet.h>
  8. #include <string.h>
  9. #include <stdlib.h>
  10. #include <stdio.h>
  11. #include <errno.h>
  13. static void
  14. echo_read_cb(struct bufferevent *bev, void *ctx)
  15. {
  16.     /* 获取bufferevent中的读和写的指针 */
  17.     /* This callback is invoked when there is data to read on bev. */
  18.     struct evbuffer *input = bufferevent_get_input(bev);
  19.     struct evbuffer *output = bufferevent_get_output(bev);
  20.     /* 把读入的数据全部复制到写内存中 */
  21.     /* Copy all the data from the input buffer to the output buffer. */
  22.     evbuffer_add_buffer(output, input);
  23. }
  25. static void echo_event_cb(struct bufferevent *bev, short events, void *ctx)
  26. {
  27.     if (events & BEV_EVENT_ERROR)
  28.         perror("Error from bufferevent");
  29.     if (events & (BEV_EVENT_EOF | BEV_EVENT_ERROR)) {
  30.         bufferevent_free(bev);
  31.     }
  32. }
  34. static void accept_conn_cb(struct evconnlistener *listener,evutil_socket_t fd, struct sockaddr *address, int socklen,void *ctx)
  35. {
  36.     /* 初始化一个bufferevent用于数据的写入和读取，首先需要从Listerner中获取event_base */
  37.     /* We got a new connection! Set up a bufferevent for it. */
  38.     struct event_base *base = evconnlistener_get_base(listener);
  39.     struct bufferevent *bev = bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE);
  40.     /*设置buferevent的回调函数，这里设置了读和事件的回调函数*/
  41.     bufferevent_setcb(bev, echo_read_cb, NULL, echo_event_cb, NULL);
  42.     /* 启用该bufevent写和读 */
  43.      bufferevent_enable(bev, EV_READ|EV_WRITE);
  44. }
  46. static void
  47. accept_error_cb(struct evconnlistener *listener, void *ctx)
  48. {
  49.     struct event_base *base = evconnlistener_get_base(listener);
  50.     int err = EVUTIL_SOCKET_ERROR();
  51.     fprintf(stderr, "Got an error %d (%s) on the listener. ""Shutting down.\n", err, evutil_socket_error_to_string(err));
  53.     event_base_loopexit(base, NULL);
  54. }
  56. int
  57. main(int argc, char **argv)
  58. {
  59.     struct event_base *base;
  60.     struct evconnlistener *listener;
  61.     struct sockaddr_in sin;
  63.     int port = 8111;
  65.     /*
  66.     if (argc > 1) {
  67.         port = atoi(argv[1]);
  68.     }
  69.     if (port<=0 || port>65535) {
  70.         puts("Invalid port");
  71.         return 1;
  72.     }*/
  75.     //use threads
  76.     //evthread_use_pthreads();
  78.     base = event_base_new(); /* 初始化event_base */
  79.     if (!base) {
  80.         puts("Couldn't open event base");
  81.         return 1;
  82.     }
  84.     /*初始化绑定地址*/
  85.     /*Clear the sockaddr before using it, 
  86.      * in case there are extra platform-specific fields 
  87.      * that can mess us up.
  88.      */
  89.     memset(&sin, 0, sizeof(sin));
  90.     /*This is an INET address */
  91.     sin.sin_family = AF_INET;
  92.     /*Listen on 0.0.0.0*/
  93.     sin.sin_addr.s_addr = INADDR_ANY;
  94.     /*Listen on the given port.*/
  95.     sin.sin_port = htons(port);
  97.     /* 初始化evconnlistener(绑定地址、设置回调函数以及连接属性) */
  98.     listener = evconnlistener_new_bind(base, accept_conn_cb, NULL, LEV_OPT_CLOSE_ON_FREE|LEV_OPT_REUSEABLE, -1,(struct sockaddr*)&sin, sizeof(sin));
  99.     if (!listener) {
  100.         perror("Couldn't create listener");
  101.         return 1;
  102.     }
  104.     /* 设置Listen错误回调函数 */
  105.     evconnlistener_set_error_cb(listener, accept_error_cb);
  107.     /* 开始accept进入循环 */
  108.     event_base_dispatch(base);
  109.     return 0;
  110. }
  1. gcc -o tcp_server tcp_server.c -levent
  2. ./tcp_server

运行客户端

  1. ubuntu@VM-8-4-ubuntu:~/lichao_audio_video/server_webrtc/mediaserver/02_network/05_tcp_client$ ./tcp_client 
  2. success to connect server...
  3. <<<<send message:dsfaas
  4. >>> echo message:dsfaas  （ps:这是服务端回复的内容）
  5. <<<<send message:

7-3 作业

1、libevent实现对UDP的处理
2、libuv实现对UDP的处理