Libevent使用实例1 (简单)

雨点打透心脏的1/2处 2022-05-11 08:40 278阅读 0赞

客户端：

#include<event2/event-config.h>
    
    #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;
    	}
    
    	//两个参数依次是服务器端的IP地址，端口号
    	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();
    
    	//监听读事件
    	struct event* ev_sockfd = event_new(base,sockfd,EV_READ | EV_PERSIST, socket_read_cb, NULL);
    	
    	event_add(ev_sockfd, NULL);	//正式添加事件
    
    	//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);
    																			//回调函数：参数是：fd,event,arg
    
    	event_add(ev_cmd,NULL);		//添加事件
    
    	event_base_dispatch(base);	//进入循环，等待就绪事件并执行事件处理
    	
    	printf("finished\n");
    	
    	return 0;
    }
    
    
    void cmd_msg_cb(int fd, short events, void* arg) { // fd:STDIN_FILENO,event:EV_READ | EV_PERSIST,arg:sockfd;
    											      //该回调函数作用是从标准输入读到msg,再把msg的数据发送给sockfd(服务器端)
    	char msg[1024];
    
    	int ret = read(fd,msg,sizeof(msg));			//ret是读取的长度
    	if(ret <= 0) {
    		perror("read fail");
    		exit(1);
    	}
    
    	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) { //fd:sockfd,event:EV_READ | EV_PERSIST,arg是空
    	char msg[1024];
    
    	//为了简单起见，不考虑写一半数据的情况 
    	int len = read(fd,msg,sizeof(msg)-1);
    	if(len <= 0) {
    		perror("read fail");
    		exit(1);
    	}
    
    	msg[len] = '\0';
    	
    	printf("recv %s fron 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);	//将IP地址转换为网络字节序整数
    
    
    	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);	//设置成不阻塞
    
    	return sockfd;
    }

gcc -o primary\_client primary\_client.c \-levent

服务器端：

#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);//将base参数传给回调函数
        
    	event_add(ev_listen, NULL);
    
        event_base_dispatch(base);
    
        return 0;
    }
    
    
    
    void accept_cb(int fd, short events, void* arg)	//fd:listener , events: EV_READ | EV_PERSIST, arg:base;
    {
        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 = (struct event_base*)arg;	//arg传入的实参就是base，但是是void*,所以强制转换回来
    
        //仅仅是为了动态创建一个event结构体
        struct event *ev = event_new(NULL, -1, 0, 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); //监听读事件
    	//event_assign等价于：struct event* ev = event_new(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) { //fd:sockfd, events:EV_READ | EV_PERSIST, arg:ev,监听读事件的回调函数
    	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);	//将msg字符串复制到reply_msg的末尾
    
    	write(fd,reply_msg,strlen(reply_msg) );			//向客户端发送回复已收到的数据
    }
    
    
    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;
    
    	//允许多次绑定同一地址要用在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 = 0;
    	sin.sin_port = htons(port);
    
    	if(bind(listener, (SA*)&sin, sizeof(sin) ) < 0)
    		goto error;
    
    	if(listen(listener,listen_num) < 0)
    		goto error;
    
    	//跨平台同一接口，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 -1;
    }

gcc -o primary\_server.c primary\_server \-levent

**注意：**

编译时要在编译语句后面加上 **-levent**  
表示要链接event静态函数库,如果没有这一句,那么整个链接将会出错,类似与下面的结局：

main.cpp:(.text+0x2c)：对‘evutil_make_listen_socket_reuseable’未定义的引用
    main.cpp:(.text+0xec)：对‘evutil_make_socket_nonblocking’未定义的引用
    main.cpp:(.text+0xf1)：对‘event_base_new’未定义的引用
    main.cpp:(.text+0x13f)：对‘event_new’未定义的引用
    main.cpp:(.text+0x154)：对‘event_add’未定义的引用
    main.cpp:(.text+0x160)：对‘event_base_dispatch’未定义的引用
    main.cpp:(.text+0x16c)：对‘event_base_free’未定义的引用
    /tmp/ccFk4bSL.o：在函数‘do_accept(int, short, void*)’中：
    main.cpp:(.text+0x22e)：对‘bufferevent_socket_new’未定义的引用
    main.cpp:(.text+0x254)：对‘bufferevent_setcb’未定义的引用
    main.cpp:(.text+0x265)：对‘bufferevent_enable’未定义的引用
    /tmp/ccFk4bSL.o：在函数‘read_cb(bufferevent*, void*)’中：
    main.cpp:(.text+0x28f)：对‘bufferevent_getfd’未定义的引用
    main.cpp:(.text+0x2f5)：对‘bufferevent_write’未定义的引用
    main.cpp:(.text+0x313)：对‘bufferevent_read’未定义的引用
    /tmp/ccFk4bSL.o：在函数‘error_cb(bufferevent*, short, void*)’中：
    main.cpp:(.text+0x357)：对‘bufferevent_getfd’未定义的引用
    main.cpp:(.text+0x408)：对‘bufferevent_free’未定义的引用

运行结果:

客户端：

![70][]

服务器：

![70 1][]

[70]: /images/20220511/034f9bb1a9fd4c05ac634674cdc90c14.png
[70 1]: /images/20220511/efa2afe1dd0a41118b8cd17a699ff381.png