Linux下Libevent安裝和簡單實用

前言

Libevent 是一個用C語言編寫的、輕量級的開源高性能事件通知庫，主要有以下幾個亮點：事件驅動（ event-driven），高性能;輕量級，專注於網絡，不如 ACE 那么臃腫龐大；源代碼相當精煉、易讀；跨平台，支持 Windows、 Linux、 *BSD 和 Mac Os；支持多種 I/O 多路復用技術， epoll、 poll、 dev/poll、 select 和 kqueue 等；支持 I/O，定時器和信號等事件；注冊事件優先級。Libevent 已經被廣泛的應用，作為底層的網絡庫；比如 memcached、 Vomit、 Nylon、 Netchat等

Libevent下載和安裝

1. 下載
官方網站：http://libevent.org/，目前最新版是2.1
下載壓縮包名為 libevent-2.1.11-stable.tar.gz
2. 解壓

tar -zxvf libevent-2.1.11-stable.tar.gz 

3. 配置安裝路徑

cd libevent-2.1.11-stable
./configure

也可以指定后綴，比如路徑為./configure -prefix=/usr

4. 編譯安裝

make
make install

5. 測試是否已安裝

ls -al /usr/local/lib | grep libevent

6. 使用樣例程序進行測試

cd sample/

此目錄下，有很多樣例，可以進行測試，也可以進行學習

使用Libevent編寫簡單的程序和編譯

使用libevent庫開發的程序，默認編譯需要加入-levent
問題：如果在編譯或運行時候發現出現：error while loading shared libraries: libevent-2.1.so.7: cannot open shared object file: No such file or directory
則需要查看libevent-2.1.so.7是否存在，需要先安裝mlocate

locate libevent-2.1.so.7

結果： 系統已經安裝了該模塊，在路徑 /usr/local/lib/
映射libevent-2.1.so.7到lib64下即可

ln -s /usr/local/lib/libevent-2.1.so.7 /usr/lib64/libevent-2.1.so.7

然后就可以正常的運行了

Libevent程序實例

初等

客戶端代碼

#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 < 3 )
    {
        printf("please input 2 parameter\n");
        return -1;
    }
    //兩個參數依次是服務器端的IP地址、端口號
    int sockfd = tcp_connect_server(argv[1], atoi(argv[2]));
    if( sockfd == -1)
    {
        perror("tcp_connect error ");
        return -1;
    }
    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);
    //監聽終端輸入事件
    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 0;
}

void cmd_msg_cb(int fd, short events, void* arg)
{
    char msg[1024];
    int ret = read(fd, msg, sizeof(msg));
    if( ret <= 0 )
    {
        perror("read fail ");
        exit(1);
    }
    int sockfd = *((int*)arg);
    //把終端的消息發送給服務器端
    //為了簡單起見，不考慮寫一半數據的情況
    write(sockfd, msg, ret);
}

void socket_read_cb(int fd, short events, void *arg)
{
    char msg[1024];
    //為了簡單起見，不考慮讀一半數據的情況
    int len = read(fd, msg, sizeof(msg)-1);
    if( len <= 0 )
    {
        perror("read fail ");
        exit(1);
    }
    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, 0, 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 == 0 ) //the server_ip is not valid value
    {
        errno = EINVAL;
        return -1;
    }
    sockfd = ::socket(PF_INET, SOCK_STREAM, 0);
    if( sockfd == -1 )
        return sockfd;
    status = ::connect(sockfd, (SA*)&server_addr, sizeof(server_addr) );
   
    if( status == -1 )
    {
        save_errno = errno;
        ::close(sockfd);
        errno = save_errno; //the close may be error
        return -1;
    }
    evutil_make_socket_nonblocking(sockfd);
    return sockfd;
}

服務器代碼

#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(9999, 10);
    if( listener == -1 )
    {
        perror(" tcp_server_init error ");
        return -1;
    }
    struct event_base* base = event_base_new();
    //添加監聽客戶端請求連接事件
    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 0;
}

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;
    //僅僅是為了動態創建一個event結構體
    struct event *ev = event_new(NULL, -1, 0, NULL, NULL);
    //將動態創建的結構體作為event的回調參數
    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[4096];
    struct event *ev = (struct event*)arg;
    int len = read(fd, msg, sizeof(msg) - 1);
    if( len <= 0 )
    {
        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[4096] = "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, 0);
    if( listener == -1 )
        return -1;
    //允許多次綁定同一個地址。要用在socket和bind之間
    evutil_make_listen_socket_reuseable(listener);
    struct sockaddr_in sin;
    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = 0;
    sin.sin_port = htons(port);
    if( ::bind(listener, (SA*)&sin, sizeof(sin)) < 0 )
        goto error;
    if( ::listen(listener, listen_num) < 0)
        goto error;
    //跨平台統一接口，將套接字設置為非阻塞狀態
    evutil_make_socket_nonblocking(listener);
    return listener;
    error:
        errno_save = errno;
        evutil_closesocket(listener);
        errno = errno_save;
        return -1;
}

中等

客戶端代碼

#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 < 3 )
    {
        printf("please input 2 parameter\n");
        return -1;
    }
    //兩個參數依次是服務器端的IP地址、端口號
    int sockfd = tcp_connect_server(argv[1], atoi(argv[2]));
    if( sockfd == -1)
    {
        perror("tcp_connect error ");
        return -1;
    }
    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);
    //監聽終端輸入事件
    struct event* ev_cmd = event_new(base, STDIN_FILENO,
                                      EV_READ | EV_PERSIST, cmd_msg_cb,
                                      (void*)bev);
    event_add(ev_cmd, NULL);
    //當socket關閉時會用到回調參數
    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 0;
}

void cmd_msg_cb(int fd, short events, void* arg)
{
    char msg[1024];
    int ret = read(fd, msg, sizeof(msg));
    if( ret < 0 )
    {
        perror("read fail ");
        exit(1);
    }
    struct bufferevent* bev = (struct bufferevent*)arg;
    //把終端的消息發送給服務器端
    bufferevent_write(bev, msg, ret);
}

void server_msg_cb(struct bufferevent* bev, void* arg)
{
    char msg[1024];
    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");
    //這將自動close套接字和free讀寫緩沖區
    bufferevent_free(bev);
    struct event *ev = (struct event*)arg;
    //因為socket已經沒有，所以這個event也沒有存在的必要了
    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, 0, 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 == 0 ) //the server_ip is not valid value
    {
        errno = EINVAL;
        return -1;
    }
    sockfd = ::socket(PF_INET, SOCK_STREAM, 0);
    if( sockfd == -1 )
        return sockfd;
    status = ::connect(sockfd, (SA*)&server_addr, sizeof(server_addr) );
    if( status == -1 )
    {
        save_errno = errno;
        ::close(sockfd);
        errno = save_errno; //the close may be error
        return -1;
    }
    evutil_make_socket_nonblocking(sockfd);
    return sockfd;
}

服務器代碼

#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(9999, 10);
    if( listener == -1 )
    {
        perror(" tcp_server_init error ");
        return -1;
    }
    struct event_base* base = event_base_new();
    //添加監聽客戶端請求連接事件
    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 0;
}

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[4096];
    size_t len = bufferevent_read(bev, msg, sizeof(msg));
    msg[len] = '\0';
    printf("recv the client msg: %s", msg);
    char reply_msg[4096] = "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");
    //這將自動close套接字和free讀寫緩沖區
    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, 0);
    if( listener == -1 )
        return -1;
    //允許多次綁定同一個地址。要用在socket和bind之間
    evutil_make_listen_socket_reuseable(listener);
    struct sockaddr_in sin;
    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = 0;
    sin.sin_port = htons(port);
    if( ::bind(listener, (SA*)&sin, sizeof(sin)) < 0 )
        goto error;
    if( ::listen(listener, listen_num) < 0)
        goto error;
    //跨平台統一接口，將套接字設置為非阻塞狀態
    evutil_make_socket_nonblocking(listener);
    return listener;
    error:
        errno_save = errno;
        evutil_closesocket(listener);
        errno = errno_save;
        return -1;
}

高等

客戶端代碼

#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 < 3 )
    {
        //兩個參數依次是服務器端的IP地址、端口號
        printf("please input 2 parameter\n");
        return -1;
    }
    struct event_base *base = event_base_new();
    struct bufferevent* bev = bufferevent_socket_new(base, -1,
                                                     BEV_OPT_CLOSE_ON_FREE);
    //監聽終端輸入事件
    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, 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);
    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 0;
}

void cmd_msg_cb(int fd, short events, void* arg)
{
    char msg[1024];
    int ret = read(fd, msg, sizeof(msg));
    if( ret < 0 )
    {
        perror("read fail ");
        exit(1);
    }
    struct bufferevent* bev = (struct bufferevent*)arg;
    //把終端的消息發送給服務器端
    bufferevent_write(bev, msg, ret);
}

void server_msg_cb(struct bufferevent* bev, void* arg)
{
    char msg[1024];
    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 ;
    }
    //這將自動close套接字和free讀寫緩沖區
    bufferevent_free(bev);
    struct event *ev = (struct event*)arg;
    event_free(ev);
}

服務器代碼

#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, 0, sizeof(struct sockaddr_in));  
    sin.sin_family = AF_INET;  
    sin.sin_port = htons(9999);  
    event_base *base = event_base_new();  
    evconnlistener *listener  
            = evconnlistener_new_bind(base, listener_cb, base,  
                                      LEV_OPT_REUSEABLE|LEV_OPT_CLOSE_ON_FREE,  
                                      10, (struct sockaddr*)&sin,  
                                      sizeof(struct sockaddr_in));  
    event_base_dispatch(base);  
    evconnlistener_free(listener);  
    event_base_free(base);  
    return 0;  
}  

//一個新客戶端連接上服務器了  
//當此函數被調用時，libevent已經幫我們accept了這個客戶端。該客戶端的
//文件描述符為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;  
    //為這個客戶端分配一個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[4096];  
    size_t len = bufferevent_read(bev, msg, sizeof(msg)-1 );  
    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");  
    //這將自動close套接字和free讀寫緩沖區  
    bufferevent_free(bev);  
}  

關於libevent編程時的一些疑問可以閱讀《libevent編程疑難解答》。假如讀者還想了解libevent的具體實現，可以閱讀《libevent源碼分析》系統文章。

更多文章參考：
http://blog.csdn.net/luotuo44/article/details/39547391
https:/blog.csdn.net/luotuo44/article/category/2435521