转载请注明出处：http://blog.csdn.net/luotuo44/article/details/39670221

本文从简单到复杂，展示如何使用libevent。网上的许多例子都是只有服务器端的，本文里面客户端和服务器端都有，以飨读者。

关于libevent编程时的一些疑问可以阅读《libevent编程疑难解答》。假如读者还想了解libevent的具体实现，可以阅读《libevent源码分析》系统文章。

不说这么多了，直接上代码。

初等：

客户端代码：

#include<sys/types.h>

#include<sys/socket.h>

#include<netinet/in.h>

#include<arpa/inet.h>

#include<errno.h>

#include<unistd.h>  

#include<stdio.h>

#include<string.h>

#include<stdlib.h>  

#include<event.h>

#include<event2/util.h>  

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

void cmd_msg_cb(int fd, short events, void* arg);

void socket_read_cb(int fd, short events, void *arg);  

int main(int argc, char** argv)

{

    if( argc <  )

    {

        printf("please input 2 parameter\n");

        return -;

    }  

    //两个参数依次是服务器端的IP地址、端口号

    int sockfd = tcp_connect_server(argv[], atoi(argv[]));

    if( sockfd == -)

    {

        perror("tcp_connect error ");

        return -;

    }  

    printf("connect to server successful\n");  

    struct event_base* base = event_base_new();  

    struct event *ev_sockfd = event_new(base, sockfd,

                                        EV_READ | EV_PERSIST,

                                        socket_read_cb, NULL);

    event_add(ev_sockfd, NULL);  

    //监听终端输入事件

    struct event* ev_cmd = event_new(base, STDIN_FILENO,

                                      EV_READ | EV_PERSIST, cmd_msg_cb,

                                      (void*)&sockfd);  

    event_add(ev_cmd, NULL);  

    event_base_dispatch(base);  

    printf("finished \n");

    return ;

}  

void cmd_msg_cb(int fd, short events, void* arg)

{

    char msg[];  

    int ret = read(fd, msg, sizeof(msg));

    if( ret <=  )

    {

        perror("read fail ");

        exit();

    }  

    int sockfd = *((int*)arg);  

    //把终端的消息发送给服务器端

    //为了简单起见，不考虑写一半数据的情况

    write(sockfd, msg, ret);

}  

void socket_read_cb(int fd, short events, void *arg)

{

    char msg[];  

    //为了简单起见，不考虑读一半数据的情况

    int len = read(fd, msg, sizeof(msg)-);

    if( len <=  )

    {

        perror("read fail ");

        exit();

    }  

    msg[len] = '\0';  

    printf("recv %s from server\n", msg);

}  

typedef struct sockaddr SA;

int tcp_connect_server(const char* server_ip, int port)

{

    int sockfd, status, save_errno;

    struct sockaddr_in server_addr;  

    memset(&server_addr, , sizeof(server_addr) );  

    server_addr.sin_family = AF_INET;

    server_addr.sin_port = htons(port);

    status = inet_aton(server_ip, &server_addr.sin_addr);  

    if( status ==  ) //the server_ip is not valid value

    {

        errno = EINVAL;

        return -;

    }  

    sockfd = ::socket(PF_INET, SOCK_STREAM, );

    if( sockfd == - )

        return sockfd;  

    status = ::connect(sockfd, (SA*)&server_addr, sizeof(server_addr) );  

    if( status == - )

    {

        save_errno = errno;

        ::close(sockfd);

        errno = save_errno; //the close may be error

        return -;

    }  

    evutil_make_socket_nonblocking(sockfd);  

    return sockfd;

}

服务器端代码：

#include<stdio.h>

#include<string.h>

#include<errno.h>  

#include<unistd.h>

#include<event.h>  

void accept_cb(int fd, short events, void* arg);

void socket_read_cb(int fd, short events, void *arg);  

int tcp_server_init(int port, int listen_num);  

int main(int argc, char** argv)

{  

    int listener = tcp_server_init(, );

    if( listener == - )

    {

        perror(" tcp_server_init error ");

        return -;

    }  

    struct event_base* base = event_base_new();  

    //添加监听客户端请求连接事件

    struct event* ev_listen = event_new(base, listener, EV_READ | EV_PERSIST,

                                        accept_cb, base);

    event_add(ev_listen, NULL);  

    event_base_dispatch(base);  

    return ;

}  

void accept_cb(int fd, short events, void* arg)

{

    evutil_socket_t sockfd;  

    struct sockaddr_in client;

    socklen_t len = sizeof(client);  

    sockfd = ::accept(fd, (struct sockaddr*)&client, &len );

    evutil_make_socket_nonblocking(sockfd);  

    printf("accept a client %d\n", sockfd);  

    struct event_base* base = (event_base*)arg;  

    //仅仅是为了动态创建一个event结构体

    struct event *ev = event_new(NULL, -, , NULL, NULL);

    //将动态创建的结构体作为event的回调参数

    event_assign(ev, base, sockfd, EV_READ | EV_PERSIST,

                 socket_read_cb, (void*)ev);  

    event_add(ev, NULL);

}  

void socket_read_cb(int fd, short events, void *arg)

{

    char msg[];

    struct event *ev = (struct event*)arg;

    int len = read(fd, msg, sizeof(msg) - );  

    if( len <=  )

    {

        printf("some error happen when read\n");

        event_free(ev);

        close(fd);

        return ;

    }  

    msg[len] = '\0';

    printf("recv the client msg: %s", msg);  

    char reply_msg[] = "I have recvieced the msg: ";

    strcat(reply_msg + strlen(reply_msg), msg);  

    write(fd, reply_msg, strlen(reply_msg) );

}  

typedef struct sockaddr SA;

int tcp_server_init(int port, int listen_num)

{

    int errno_save;

    evutil_socket_t listener;  

    listener = ::socket(AF_INET, SOCK_STREAM, );

    if( listener == - )

        return -;  

    //允许多次绑定同一个地址。要用在socket和bind之间

    evutil_make_listen_socket_reuseable(listener);  

    struct sockaddr_in sin;

    sin.sin_family = AF_INET;

    sin.sin_addr.s_addr = ;

    sin.sin_port = htons(port);  

    if( ::bind(listener, (SA*)&sin, sizeof(sin)) <  )

        goto error;  

    if( ::listen(listener, listen_num) < )

        goto error;  

    //跨平台统一接口，将套接字设置为非阻塞状态

    evutil_make_socket_nonblocking(listener);  

    return listener;  

    error:

        errno_save = errno;

        evutil_closesocket(listener);

        errno = errno_save;  

        return -;

}

中等：

客户端代码：

#include<sys/types.h>

#include<sys/socket.h>

#include<netinet/in.h>

#include<arpa/inet.h>

#include<errno.h>

#include<unistd.h>  

#include<stdio.h>

#include<string.h>

#include<stdlib.h>  

#include<event.h>

#include<event2/bufferevent.h>

#include<event2/buffer.h>

#include<event2/util.h>  

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);  

int main(int argc, char** argv)

{

    if( argc <  )

    {

        printf("please input 2 parameter\n");

        return -;

    }  

    //两个参数依次是服务器端的IP地址、端口号

    int sockfd = tcp_connect_server(argv[], atoi(argv[]));

    if( sockfd == -)

    {

        perror("tcp_connect error ");

        return -;

    }  

    printf("connect to server successful\n");  

    struct event_base* base = event_base_new();  

    struct bufferevent* bev = bufferevent_socket_new(base, sockfd,

                                                     BEV_OPT_CLOSE_ON_FREE);  

    //监听终端输入事件

    struct event* ev_cmd = event_new(base, STDIN_FILENO,

                                      EV_READ | EV_PERSIST, cmd_msg_cb,

                                      (void*)bev);

    event_add(ev_cmd, NULL);  

    //当socket关闭时会用到回调参数

    bufferevent_setcb(bev, server_msg_cb, NULL, event_cb, (void*)ev_cmd);

    bufferevent_enable(bev, EV_READ | EV_PERSIST);  

    event_base_dispatch(base);  

    printf("finished \n");

    return ;

}  

void cmd_msg_cb(int fd, short events, void* arg)

{

    char msg[];  

    int ret = read(fd, msg, sizeof(msg));

    if( ret <  )

    {

        perror("read fail ");

        exit();

    }  

    struct bufferevent* bev = (struct bufferevent*)arg;  

    //把终端的消息发送给服务器端

    bufferevent_write(bev, msg, ret);

}  

void server_msg_cb(struct bufferevent* bev, void* arg)

{

    char msg[];  

    size_t len = bufferevent_read(bev, msg, sizeof(msg));

    msg[len] = '\0';  

    printf("recv %s from server\n", msg);

}  

void event_cb(struct bufferevent *bev, short event, void *arg)

{  

    if (event & BEV_EVENT_EOF)

        printf("connection closed\n");

    else if (event & BEV_EVENT_ERROR)

        printf("some other error\n");  

    //这将自动close套接字和free读写缓冲区

    bufferevent_free(bev);  

    struct event *ev = (struct event*)arg;

    //因为socket已经没有，所以这个event也没有存在的必要了

    event_free(ev);

}  

typedef struct sockaddr SA;

int tcp_connect_server(const char* server_ip, int port)

{

    int sockfd, status, save_errno;

    struct sockaddr_in server_addr;  

    memset(&server_addr, , sizeof(server_addr) );  

    server_addr.sin_family = AF_INET;

    server_addr.sin_port = htons(port);

    status = inet_aton(server_ip, &server_addr.sin_addr);  

    if( status ==  ) //the server_ip is not valid value

    {

        errno = EINVAL;

        return -;

    }  

    sockfd = ::socket(PF_INET, SOCK_STREAM, );

    if( sockfd == - )

        return sockfd;  

    status = ::connect(sockfd, (SA*)&server_addr, sizeof(server_addr) );  

    if( status == - )

    {

        save_errno = errno;

        ::close(sockfd);

        errno = save_errno; //the close may be error

        return -;

    }  

    evutil_make_socket_nonblocking(sockfd);  

    return sockfd;

}

服务器端代码：

#include<stdio.h>

#include<string.h>

#include<errno.h>  

#include<event.h>

#include<event2/bufferevent.h>  

void accept_cb(int fd, short events, void* arg);

void socket_read_cb(bufferevent* bev, void* arg);

void event_cb(struct bufferevent *bev, short event, void *arg);

int tcp_server_init(int port, int listen_num);  

int main(int argc, char** argv)

{  

    int listener = tcp_server_init(, );

    if( listener == - )

    {

        perror(" tcp_server_init error ");

        return -;

    }  

    struct event_base* base = event_base_new();  

    //添加监听客户端请求连接事件

    struct event* ev_listen = event_new(base, listener, EV_READ | EV_PERSIST,

                                        accept_cb, base);

    event_add(ev_listen, NULL);  

    event_base_dispatch(base);

    event_base_free(base);  

    return ;

}  

void accept_cb(int fd, short events, void* arg)

{

    evutil_socket_t sockfd;  

    struct sockaddr_in client;

    socklen_t len = sizeof(client);  

    sockfd = ::accept(fd, (struct sockaddr*)&client, &len );

    evutil_make_socket_nonblocking(sockfd);  

    printf("accept a client %d\n", sockfd);  

    struct event_base* base = (event_base*)arg;  

    bufferevent* bev = bufferevent_socket_new(base, sockfd, BEV_OPT_CLOSE_ON_FREE);

    bufferevent_setcb(bev, socket_read_cb, NULL, event_cb, arg);  

    bufferevent_enable(bev, EV_READ | EV_PERSIST);

}  

void socket_read_cb(bufferevent* bev, void* arg)

{

    char msg[];  

    size_t len = bufferevent_read(bev, msg, sizeof(msg));  

    msg[len] = '\0';

    printf("recv the client msg: %s", msg);  

    char reply_msg[] = "I have recvieced the msg: ";  

    strcat(reply_msg + strlen(reply_msg), msg);

    bufferevent_write(bev, reply_msg, strlen(reply_msg));

}  

void event_cb(struct bufferevent *bev, short event, void *arg)

{  

    if (event & BEV_EVENT_EOF)

        printf("connection closed\n");

    else if (event & BEV_EVENT_ERROR)

        printf("some other error\n");  

    //这将自动close套接字和free读写缓冲区

    bufferevent_free(bev);

}  

typedef struct sockaddr SA;

int tcp_server_init(int port, int listen_num)

{

    int errno_save;

    evutil_socket_t listener;  

    listener = ::socket(AF_INET, SOCK_STREAM, );

    if( listener == - )

        return -;  

    //允许多次绑定同一个地址。要用在socket和bind之间

    evutil_make_listen_socket_reuseable(listener);  

    struct sockaddr_in sin;

    sin.sin_family = AF_INET;

    sin.sin_addr.s_addr = ;

    sin.sin_port = htons(port);  

    if( ::bind(listener, (SA*)&sin, sizeof(sin)) <  )

        goto error;  

    if( ::listen(listener, listen_num) < )

        goto error;  

    //跨平台统一接口，将套接字设置为非阻塞状态

    evutil_make_socket_nonblocking(listener);  

    return listener;  

    error:

        errno_save = errno;

        evutil_closesocket(listener);

        errno = errno_save;  

        return -;

}

高等：

客户端代码：

#include<sys/types.h>

#include<sys/socket.h>

#include<netinet/in.h>

#include<arpa/inet.h>

#include<errno.h>

#include<unistd.h>  

#include<stdio.h>

#include<string.h>

#include<stdlib.h>  

#include<event.h>

#include<event2/bufferevent.h>

#include<event2/buffer.h>

#include<event2/util.h>  

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);  

int main(int argc, char** argv)

{

    if( argc <  )

    {

        //两个参数依次是服务器端的IP地址、端口号

        printf("please input 2 parameter\n");

        return -;

    }  

    struct event_base *base = event_base_new();  

    struct bufferevent* bev = bufferevent_socket_new(base, -,

                                                     BEV_OPT_CLOSE_ON_FREE);  

    //监听终端输入事件

    struct event* ev_cmd = event_new(base, STDIN_FILENO,

                                     EV_READ | EV_PERSIST,

                                     cmd_msg_cb, (void*)bev);  

    event_add(ev_cmd, NULL);  

    struct sockaddr_in server_addr;  

    memset(&server_addr, , sizeof(server_addr) );  

    server_addr.sin_family = AF_INET;

    server_addr.sin_port = htons(atoi(argv[]));

    inet_aton(argv[], &server_addr.sin_addr);  

    bufferevent_socket_connect(bev, (struct sockaddr *)&server_addr,

                               sizeof(server_addr));  

    bufferevent_setcb(bev, server_msg_cb, NULL, event_cb, (void*)ev_cmd);

    bufferevent_enable(bev, EV_READ | EV_PERSIST);  

    event_base_dispatch(base);  

    printf("finished \n");

    return ;

}  

void cmd_msg_cb(int fd, short events, void* arg)

{

    char msg[];  

    int ret = read(fd, msg, sizeof(msg));

    if( ret <  )

    {

        perror("read fail ");

        exit();

    }  

    struct bufferevent* bev = (struct bufferevent*)arg;  

    //把终端的消息发送给服务器端

    bufferevent_write(bev, msg, ret);

}  

void server_msg_cb(struct bufferevent* bev, void* arg)

{

    char msg[];  

    size_t len = bufferevent_read(bev, msg, sizeof(msg));

    msg[len] = '\0';  

    printf("recv %s from server\n", msg);

}  

void event_cb(struct bufferevent *bev, short event, void *arg)

{  

    if (event & BEV_EVENT_EOF)

        printf("connection closed\n");

    else if (event & BEV_EVENT_ERROR)

        printf("some other error\n");

    else if( event & BEV_EVENT_CONNECTED)

    {

        printf("the client has connected to server\n");

        return ;

    }  

    //这将自动close套接字和free读写缓冲区

    bufferevent_free(bev);  

    struct event *ev = (struct event*)arg;

    event_free(ev);

}

服务器端代码：

#include<netinet/in.h>

#include<sys/socket.h>

#include<unistd.h>    

#include<stdio.h>

#include<string.h>    

#include<event.h>

#include<listener.h>

#include<bufferevent.h>

#include<thread.h>    

void listener_cb(evconnlistener *listener, evutil_socket_t fd,

                 struct sockaddr *sock, int socklen, void *arg);    

void socket_read_cb(bufferevent *bev, void *arg);

void socket_event_cb(bufferevent *bev, short events, void *arg);    

int main()

{

    //evthread_use_pthreads();//enable threads    

    struct sockaddr_in sin;

    memset(&sin, , sizeof(struct sockaddr_in));

    sin.sin_family = AF_INET;

    sin.sin_port = htons();    

    event_base *base = event_base_new();

    evconnlistener *listener

            = evconnlistener_new_bind(base, listener_cb, base,

                                      LEV_OPT_REUSEABLE|LEV_OPT_CLOSE_ON_FREE,

                                      , (struct sockaddr*)&sin,

                                      sizeof(struct sockaddr_in));    

    event_base_dispatch(base);    

    evconnlistener_free(listener);

    event_base_free(base);    

    return ;

}    

//一个新客户端连接上服务器了

//当此函数被调用时，libevent已经帮我们accept了这个客户端。该客户端的

//文件描述符为fd

void listener_cb(evconnlistener *listener, evutil_socket_t fd,

                 struct sockaddr *sock, int socklen, void *arg)

{

    printf("accept a client %d\n", fd);    

    event_base *base = (event_base*)arg;    

    //为这个客户端分配一个bufferevent

    bufferevent *bev =  bufferevent_socket_new(base, fd,

                                               BEV_OPT_CLOSE_ON_FREE);    

    bufferevent_setcb(bev, socket_read_cb, NULL, socket_event_cb, NULL);

    bufferevent_enable(bev, EV_READ | EV_PERSIST);

}    

void socket_read_cb(bufferevent *bev, void *arg)

{

    char msg[];    

    size_t len = bufferevent_read(bev, msg, sizeof(msg)- );    

    msg[len] = '\0';

    printf("server read the data %s\n", msg);    

    char reply[] = "I has read your data";

    bufferevent_write(bev, reply, strlen(reply) );

}    

void socket_event_cb(bufferevent *bev, short events, void *arg)

{

    if (events & BEV_EVENT_EOF)

        printf("connection closed\n");

    else if (events & BEV_EVENT_ERROR)

        printf("some other error\n");    

    //这将自动close套接字和free读写缓冲区

    bufferevent_free(bev);

}

http://blog.csdn.net/luotuo44/article/details/39670221

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