我承認這篇文章有點標題黨，呵呵。其實就是一個能和服務器建立全雙工通信的客戶端而已，用網絡庫libevent實現。
  

    從這里也可以看出，同樣的功能，分別用epoll和libevent來比較，從代碼量和代碼清晰度來說，libevent完勝，呵呵。
  

    上代碼：
  

    #include <sys/socket.h>

#include <string.h>

#include <errno.h>

#include <stdlib.h>

#include <unistd.h>



#include <event.h>

#include <event2/event.h>



//發生了致命錯誤，輸入錯誤信息，退出程序

void error_quit(const char *str)

{

	perror(str);

	exit(1); 

}



//連接狀態改變時回調的函數

void eventcb(struct bufferevent *bev, short events, void *ptr)

{

	struct event_base *tbase = (struct event_base*)ptr;

	//如果不是連接成功的消息，就停止事件循環

	if ( !(events & BEV_EVENT_CONNECTED) ) 

	{

		bufferevent_free(bev);

		event_base_loopbreak(tbase);

		printf("The connect have been shutdown: %X\n", events);

	} 

}



//服務器傳信息過來了

void sockreadcb(struct bufferevent *bev, void *ptr)

{

	struct evbuffer *input = bufferevent_get_input(bev);

	evbuffer_write(input, STDOUT_FILENO);

}



//標準輸入傳消息過來了

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();



	//連接服務器并監聽

	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);



	//監聽標準輸入

	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);



	//開始事件循環

	event_base_dispatch(base);



	return 0;

}
  

    編譯與運行命令：

gcc mytelnet.c -o mytelnet -levent

./mytelnet 127.0.0.1 8877
  

    用于測試的服務器：
    
      http://blog.csdn.net/aaa20090987/article/details/8769585
    
  

用libevent實現簡易的telnet