我承认这篇文章有点标题党，呵呵。其实就是一个能和服务器建立全双工通信的客户端而已，用网络库libevent实现。

从这里也可以看出，同样的功能，分别用epoll和libevent来比较，从代码量和代码清晰度来说，libevent完胜，呵呵。

上代码：

#include <sys/socket.h>
#include <string.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>#include <event.h>
#include <event2/event.h>//发生了致命错误，输入错误信息，退出程序
void error_quit(const char *str)
{perror(str);exit(1);
}//连接状态改变时回调的函数
void eventcb(struct bufferevent *bev, short events, void *ptr)
{struct event_base *tbase = (struct event_base*)ptr;//如果不是连接成功的消息，就停止事件循环if ( !(events & BEV_EVENT_CONNECTED) ) {bufferevent_free(bev);event_base_loopbreak(tbase);printf("The connect have been shutdown: %X\n", events);}
}//服务器传信息过来了
void sockreadcb(struct bufferevent *bev, void *ptr)
{struct evbuffer *input = bufferevent_get_input(bev);evbuffer_write(input, STDOUT_FILENO);
}//标准输入传消息过来了
void stdreadcb(struct bufferevent *bev, void *ptr)
{struct bufferevent *sockbev = (struct bufferevent*)ptr; struct evbuffer *input = bufferevent_get_input(bev);bufferevent_write_buffer(sockbev, input);
}int main(int argc, char **argv)
{struct sockaddr_in servaddr;struct event *shellev;int res;struct event_base *base;struct bufferevent *sockbev;struct bufferevent *stdbev;if( argc != 3 )error_quit("Using: mytelnet <Address> <Port>");memset(&servaddr, 0, sizeof(servaddr));    servaddr.sin_family = AF_INET;    servaddr.sin_port = htons( atoi(argv[2]) );    res = inet_pton(AF_INET, argv[1], &servaddr.sin_addr);  if( res != 1 )error_quit("inet_pton error");   base = event_base_new();//连接服务器并监听sockbev = bufferevent_socket_new(base, -1, BEV_OPT_CLOSE_ON_FREE);res = bufferevent_socket_connect(sockbev,(struct sockaddr *)&servaddr, sizeof(servaddr));if ( res < 0 ) error_quit("connect error");bufferevent_setcb(sockbev, sockreadcb, NULL, eventcb, (void*)base);bufferevent_enable(sockbev, EV_READ);bufferevent_enable(sockbev, EV_WRITE);//监听标准输入stdbev = bufferevent_socket_new(base, STDIN_FILENO, BEV_OPT_CLOSE_ON_FREE);bufferevent_setcb(stdbev, stdreadcb, NULL, NULL, (void*)sockbev);bufferevent_enable(stdbev, EV_READ);bufferevent_enable(stdbev, EV_WRITE);//开始事件循环event_base_dispatch(base);return 0;
}

编译与运行命令：
gcc mytelnet.c -o mytelnet -levent
./mytelnet 127.0.0.1 8877

用于测试的服务器：http://blog.csdn.net/aaa20090987/article/details/8769585