用libevent实现的echo服务器及telnet客户端

以下代码在vs 2010编译通过，使用的libevent版本是：libevent-2.0.22，win7环境测试通过。

服务器实现：

1 流程图：

 2 代码：

// my_telnet.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"

#include <string.h>
#include <errno.h>
#include <stdio.h>
#include <signal.h>

#ifndef WIN32
#include <netinet/in.h>
# ifdef _XOPEN_SOURCE_EXTENDED
#  include <arpa/inet.h>
# endif
#include <sys/socket.h>
#endif
 
#include "event2/bufferevent.h"
#include "event2/buffer.h"
#include "event2/listener.h"
#include "event2/util.h"
#include "event2/event.h"
#include "event2/util.h"

#include <WinSock2.h>
//#include "MySimpleLog.h"


static const int PORT = 9995;

//读取一行输入并返回
static void conn_readcb(struct bufferevent *bev, void *user_data)
{
    //MY_SIMPLE_LOG_DEBUG("conn_readcb!
");

    //只有读到一行完整行才进行处理 所以这里需要检查缓冲区是否存在换行符
    //如果存在才往下走
    struct evbuffer *input = bufferevent_get_input(bev);
    struct evbuffer_ptr ptrInput;
    if ((ptrInput = evbuffer_search(input , "
", 1, NULL)).pos == -1)
    {
        return;
    }

    char line[1024] = {0};
    int nRead = 0; //已读取字节数
    int nExpect = ptrInput.pos + 1; //期望读取的字节数

    //把这一行读取出来（如果大于1024则需要分次读取）
    while (nRead < nExpect)
    {
        int nLeft = nExpect - nRead;
        int nReadOnce = min(nLeft, sizeof(line) - 1);

        int n = bufferevent_read(bev, line, nReadOnce);
        if (n <= 0)
        {
            //MY_SIMPLE_LOG_ERROR("expect to read %d bytes,but get %d.", nReadOnce, n);
            break;
        }
        line[n] = '';
        //把待发送数据添加到发送缓冲中，这里不会立即发送数据，要等conn_readcb返回后才会发送的
        bufferevent_write(bev, line, n);
        nRead += nReadOnce;
        //MY_SIMPLE_LOG_DEBUG("n = %d nRead = %d nExpect = %d! line = [%s]", n, nRead, nExpect, line);
    }

    //启动写事件，发送缓冲内容 //写事件是默认开启的，这里不需要额外设置
    //bufferevent_enable(bev, EV_WRITE | EV_PERSIST);
    
    //为避免粘包，这里要判断缓冲里面是否还有剩余数据，如果有要特别处理
    //这是因为libevent是边缘触发的，而不是水平触发
    if (evbuffer_get_length(input) != 0)
    {
        //本来是想直接激活读事件
        //但是发现要访问bufferevent未公开的成员，就不这样搞了
        //event_active(&(bev->ev_read), EV_READ, 1);
        conn_readcb(bev, user_data);
    }
}

static void conn_writecb(struct bufferevent *bev, void *user_data)
{
    //MY_SIMPLE_LOG_DEBUG("conn_writecb!");
    struct evbuffer *output = bufferevent_get_output(bev);
    if (evbuffer_get_length(output) == 0) 
    {
        //MY_SIMPLE_LOG_DEBUG("buffer writed
");
        //bufferevent_free(bev);
    }
}



static void conn_writecb_once(struct bufferevent *bev, void *user_data)
{
    //MY_SIMPLE_LOG_DEBUG("conn_writecb_once!");
    struct evbuffer *output = bufferevent_get_output(bev);
    if (evbuffer_get_length(output) == 0) 
    {
        //MY_SIMPLE_LOG_DEBUG("flushed free
");
        bufferevent_free(bev);
    }
}

static void conn_eventcb(struct bufferevent *bev, short events, void *user_data)
{
    //MY_SIMPLE_LOG_DEBUG("conn_eventcb!
");

    //判断是因为什么原因调用了此函数
    if (events & BEV_EVENT_EOF) 
    {
        //MY_SIMPLE_LOG_DEBUG("Connection closed.
");
    } 
    else if (events & BEV_EVENT_ERROR) 
    {
        //MY_SIMPLE_LOG_DEBUG("Got an error on the connection: %s
",
        //    strerror(errno));/*XXX win32*/
    }
    else if ((events & BEV_EVENT_TIMEOUT) && (events & BEV_EVENT_READING))
    {
        //发生读超时


        //超时事件发生时，会禁止相应读/写事件，需要重新注册
        //这里由于业务逻辑上认为超时就要关闭socket，就没必要这样做了
        //bufferevent_enable(bev, EV_READ | EV_PERSIST);

        //发送一个超时消息给客户端，然后就关闭bufferevent
        const char time_out_msg[] = "time out!
";
        //MY_SIMPLE_LOG_INFOR(time_out_msg);
        int n = bufferevent_write(bev, time_out_msg, sizeof(time_out_msg) - 1);
        //MY_SIMPLE_LOG_DEBUG("bufferevent_write ret %d send %d", n, int(sizeof(time_out_msg) - 1));
//        据说这个版本bufferevent_flush没实现 实测总是返回0
//         n = bufferevent_flush(bev, EV_WRITE, BEV_FINISHED);
//         //MY_SIMPLE_LOG_DEBUG("bufferevent_flush ret %d", n);

        //等写完超时信息就退出
        bufferevent_setcb(bev, NULL, conn_writecb_once, NULL, user_data);
        return;
    }
    /* None of the other events can happen here, since we haven't enabled
     * timeouts */
    bufferevent_free(bev);
}

//ctrl + c处理函数
static void signal_cb(evutil_socket_t sig, short events, void *user_data)
{
    //MY_SIMPLE_LOG_DEBUG("signal_cb!
");

    printf("to exit in 2 seconds.
");
    struct event_base *base = (struct event_base *)user_data;
    struct timeval delay = { 2, 0 };

    //MY_SIMPLE_LOG_DEBUG("Caught an interrupt signal; exiting cleanly in two seconds.
");

    event_base_loopexit(base, &delay);
}

//新连接到来处理函数
static void listener_cb(struct evconnlistener *listener, evutil_socket_t fd,
    struct sockaddr *sa, int socklen, void *user_data)
{
    //MY_SIMPLE_LOG_DEBUG("listener_cb!
");
    struct event_base *base = (struct event_base *)user_data;
    struct bufferevent *bev;

    //将该连接设置成非阻塞
    evutil_make_socket_nonblocking(fd);
    //BEV_OPT_CLOSE_ON_FREE参数让bufferevent被删除时会自动清理对应的socket
    bev = bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE);
    if (!bev) 
    {
        //MY_SIMPLE_LOG_ERROR("Error constructing bufferevent!");
        event_base_loopbreak(base);
        return;
    }
    //MY_SIMPLE_LOG_DEBUG("new connect!
");

    //开始设置各个事件的回调函数
    //最后一个参数是各个回调函数的user_data 这里不需要用到，填NULL
    //除了读写事件外，其它很多事件都是会回调conn_eventcb
    bufferevent_setcb(bev, conn_readcb, conn_writecb, conn_eventcb, NULL);

    //EV_PERSIST不设置的话读事件只会触发一次
    bufferevent_enable(bev, EV_READ | EV_PERSIST);
    //默认情况下bufferevent自动监听可读事件，如有需要可以关闭
    //关闭的情况下bufferevent_write调用后，不会真正往socket写，只保留在缓冲区
    //bufferevent_disable(bev, EV_WRITE);
    struct timeval delay = { 10, 0 };
    //读超时10秒 写超时无限
    bufferevent_set_timeouts(bev, &delay, NULL);
}

/*
基本流程：
1 新建event_base
2 生成监听socket
3 将
*/
int main(int argc, char **argv)
{
    struct event_base *base;
    struct evconnlistener *listener;
    struct event *signal_event;

    struct sockaddr_in sin;

#ifdef WIN32
    WSADATA wsa_data;
    WSAStartup(0x0201, &wsa_data);
#endif

    //MY_SIMPLE_LOG_INIT(//MY_SIMPLE_LOG_LEVEL_DEBUG);

    //初始化event_base 这个是全局唯一的
    base = event_base_new();
    if (!base) 
    {
        //MY_SIMPLE_LOG_ERROR("Could not initialize libevent!
");
        return 1;
    }
    //MY_SIMPLE_LOG_DEBUG("all inited");
    
    //往event_base新增一个event，监听连接事件
    memset(&sin, 0, sizeof(sin));
    sin.sin_family = AF_INET;
    sin.sin_port = htons(PORT);
    
    listener = evconnlistener_new_bind(base, listener_cb, (void *)base,
        LEV_OPT_REUSEABLE|LEV_OPT_CLOSE_ON_FREE, -1,
        (struct sockaddr*)&sin,
        sizeof(sin));

    if (!listener) 
    {
        //MY_SIMPLE_LOG_ERROR("Could not create a listener!
");
        event_base_free(base);
        return 1;
    }
    //MY_SIMPLE_LOG_INFOR("listener created");

    //evutil_make_socket_nonblocking(listener); //监听socket不应该设置成非阻塞
    //监听ctrl+c信号
    signal_event = evsignal_new(base, SIGINT, signal_cb, (void *)base);

    if (!signal_event || event_add(signal_event, NULL)<0) 
    {
        //MY_SIMPLE_LOG_ERROR("Could not create/add a signal event!
");
        evconnlistener_free(listener);
        event_base_free(base);
        return 1;
    }
    //MY_SIMPLE_LOG_INFOR("signal_event created");

    //MY_SIMPLE_LOG_INFOR("beging to dispatch");
    printf("beging to dispatch...
");
    //开始监听连接 这是一个内置循环的函数 event_base_loopexit函数调用才会返回
    event_base_dispatch(base);
    //MY_SIMPLE_LOG_INFOR("end dispatch
");

    //清理资源
    evconnlistener_free(listener);
    event_free(signal_event);
    event_base_free(base);

    //MY_SIMPLE_LOG_DEBUG("done
");
    return 0;
}

客户端实现：

客户端实现较简单，就不附流程图了，直接贴代码

// my_telnet.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"

#include <string.h>
#include <errno.h>
#include <stdio.h>
#include <io.h>
#include <signal.h>

#ifndef WIN32
#include <netinet/in.h>
# ifdef _XOPEN_SOURCE_EXTENDED
#  include <arpa/inet.h>
# endif
#include <sys/socket.h>
#else
#include <Ws2tcpip.h>
#endif
 
#include "event2/bufferevent.h"
#include "event2/buffer.h"
#include "event2/listener.h"
#include "event2/util.h"
#include "event2/event.h"
#include "event2/util.h"
#include <WinSock2.h>
#include <conio.h>  // _kbhit(), _getch()
//#include "MySimpleLog.h"
#include <assert.h>
static const int PORT = 9995;

int tcp_connect_server(const char* server_ip, int port);


void cmd_msg_cb(int fd, short events, void* arg);
void server_msg_cb(struct bufferevent* bev, void* arg);
void event_cb(struct bufferevent *bev, short event, void *arg);
void signal_cb(evutil_socket_t sig, short events, void *user_data);

typedef struct 
{
    struct bufferevent* bev;
    struct evbuffer *buf;
}MyTelnetParam;

int main(int argc, char** argv)
{
    if( argc < 3 )
    {
        //两个参数依次是服务器端的IP地址、端口号
        fprintf(stderr, "please input 2 parameter
");
        return -1;
    }


#ifdef WIN32
    WSADATA wsa_data;
    WSAStartup(0x0201, &wsa_data);
#endif

    //MY_SIMPLE_LOG_INIT(//MY_SIMPLE_LOG_LEVEL_DEBUG);

    struct event_base *base = event_base_new();

    //创建bufferevent 暂时不设置对应的socket
    struct bufferevent* bev = bufferevent_socket_new(base, -1,
        BEV_OPT_CLOSE_ON_FREE);
    assert(bev != NULL);
    /*
    //监听终端输入事件 这是linux的做法 win上面不能这样玩
    struct event* ev_cmd = event_new(base, _fileno(stdin),
        EV_READ | EV_PERSIST,
        cmd_msg_cb, (void*)bev);


    event_add(ev_cmd, NULL);
    */
    struct evbuffer *buf = evbuffer_new();
    assert(buf != NULL);
    MyTelnetParam param = {bev, buf};
    
    //监听终端输入事件 用超时事件 这里不用evtimer_new 因为那个事件只能触发一次
    struct event *ev_cmd = event_new(base, -1, EV_PERSIST, cmd_msg_cb, (void *)&param);
    assert(event_new != NULL);
    //每100微秒检测一次键盘输入情况 如果有输入则读取输入并发送给服务器
    //时间太短CPU占用太高，太长用户感觉有延迟
    struct timeval wait_time = {0, 100};
    event_add(ev_cmd, &wait_time);


    //监听ctrl+c信号
    struct event *signal_event = evsignal_new(base, SIGINT, signal_cb, (void *)base);
    assert(signal_event != NULL);
    event_add(signal_event, NULL);

    //服务器ip信息初始化
    struct sockaddr_in server_addr;
    memset(&server_addr, 0, sizeof(server_addr) );
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(atoi(argv[2]));
    //inet_aton(argv[1], &server_addr.sin_addr);
    server_addr.sin_addr.s_addr = inet_addr(argv[1]);

    //连接服务器，并将socket设置到bufferevent
    bufferevent_socket_connect(bev, (struct sockaddr *)&server_addr,
        sizeof(server_addr));


    bufferevent_setcb(bev, server_msg_cb, NULL, event_cb, NULL);
    bufferevent_enable(bev, EV_READ | EV_PERSIST);



    event_base_dispatch(base);
    //这将自动close套接字和free读写缓冲区
    bufferevent_free(bev);
    event_free(ev_cmd);
    event_free(signal_event);
    evbuffer_free(buf);
    event_base_free(base);

#ifdef WIN32
    WSACleanup();
#endif

    //MY_SIMPLE_LOG_DEBUG("finished 
");
    return 0;
}

void cmd_msg_cb(int fd, short events, void* arg)
{
    MyTelnetParam *param = (MyTelnetParam *)arg;
    struct bufferevent *bev = param->bev;
    struct evbuffer *buf = param->buf;
    
    //如果有键盘输入，则读取一个字符  如果不加这判断直接getch有可能会阻塞回调
    if (_kbhit())
    {
        char cInput = EOF;
        do
        {
            //读取键盘输入并回显 不用getchar 因为getchar要等用户按回车才能获取
            int nInput = (char) _getch();
            cInput = (char) nInput;
            evbuffer_add(buf, &cInput, 1);

            //这里最好用putch 不用putchar 因为有时是读取到非可视化字符，如方向键
            putch(nInput);

            //读满一行就先返回 同时换行
            if (cInput == '
')
            {
                //实际测试发现，按回车时用getch只能读取到一次按键

                cInput = '
';
                evbuffer_add(buf, &cInput, 1);
                putch(cInput);
                break;
            }     
        } while (_kbhit());

        //将buf整理成连续的内存
        //size_t nLen = evbuffer_get_length(buf);
        //evbuffer_pullup(buf, nLen);

        //往socket输出读取到的字节并移除buf现有字节
        bufferevent_write_buffer(bev, buf);
        evbuffer_drain(buf, evbuffer_get_length(buf));
    }
}

//ctrl + c处理函数
static void signal_cb(evutil_socket_t sig, short events, void *user_data)
{
    //MY_SIMPLE_LOG_DEBUG("signal_cb!
");

    printf("to exit in 2 seconds.
");
    struct event_base *base = (struct event_base *)user_data;
    struct timeval delay = { 2, 0 };

    //MY_SIMPLE_LOG_DEBUG("Caught an interrupt signal; exiting cleanly in two seconds.
");

    event_base_loopexit(base, &delay);
}

void server_msg_cb(struct bufferevent* bev, void* arg)
{
    char msg[1024 * 4];

    size_t len = bufferevent_read(bev, msg, sizeof(msg) - 1);
    msg[len] = '';

    printf("recv %d:[%s]
", (int)len, msg);
}


void event_cb(struct bufferevent *bev, short event, void *arg)
{
    if (event & BEV_EVENT_EOF)
        printf("connection closed
");
    else if (event & BEV_EVENT_ERROR)
        printf("some other error
");
    else if( event & BEV_EVENT_CONNECTED)
    {
        printf("the client has connected to server
");
        return ;
    }

    // 不等目前队列中所有回调事件完成，立即退出循环 
    // 如果等待回调事件完成再退出要用event_base_loopexit
    // 这里不能用event_base_loopexit 不然如果用户操作太快，cmd_msg_cb会报错
    event_base_loopbreak(bufferevent_get_base(bev));
}
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原文地址：https://www.cnblogs.com/kingstarer/p/6629562.html