//服务端代码：
#include <stdio.h>
#include <stdlib.h> #include <errno.h> #include <assert.h> #include <unistd.h> #include <string.h>#include <arpa/inet.h>
#include <event.h> #include <bufferevent.h> #define LISTEN_PORT 9999 #define LISTEN_BACKLOG 32 #define MAX_LINE 256 void do_accept(evutil_socket_t listener, short event, void *arg); void read_cb(struct bufferevent *bev, void *arg); void error_cb(struct bufferevent *bev, short event, void *arg); void write_cb(struct bufferevent *bev, void *arg); int main(int argc, char *argv[]) { if( argc <= 1 ) { printf( "usage: %s ip_address\n", basename( argv[0] ) ); return 1; } const char* ip = argv[1]; evutil_socket_t listener;//用于跨平台表示socket的ID（在Linux下表示的是其文件描述符） listener = socket(AF_INET, SOCK_STREAM, 0); assert(listener > 0); //用于跨平台将socket设置为可重用（实际上是将端口设为可重用) evutil_make_listen_socket_reuseable(listener); struct sockaddr_in sin; bzero( &sin, sizeof( sin ) ); sin.sin_family = AF_INET; //sin.sin_addr.s_addr = 0; inet_pton( AF_INET, ip, &sin.sin_addr ); sin.sin_port = htons(LISTEN_PORT); if (bind(listener, (struct sockaddr *)&sin, sizeof(sin)) < 0) { perror("bind"); return 1; } if (listen(listener, LISTEN_BACKLOG) < 0) { perror("listen"); return 1; } printf ("Listening...\n"); /* 用于跨平台将socket设置为非阻塞,使用bufferevent需要 */ evutil_make_socket_nonblocking(listener); //主要记录事件的相关属性 创建一个event_base struct event_base *base = event_base_new(); assert(base != NULL); /* 创建并绑定一个event */ struct event *listen_event; //参数：event_base, 监听的socket 描述符listener，事件类型及属性，绑定的回调函数，给回调函数的参数 /*EV_PERSIST参数告诉系统持续的监听sock上的读事件， 不指定这个属性的话，回调函数被触发后,事件会被删除.所以,如果不加该参数，每次要监听该事件时就要重复的调用event_add函数 */ listen_event = event_new(base, listener, EV_READ|EV_PERSIST, do_accept, (void*)base); /*通过event_add方法启动监听事件 参数：event，超时时间(struct timeval *类型的，NULL表示无超时设置) */ event_add(listen_event, NULL); /* 进入事件循环,即通过event_base_dispatch方法启动事件循环 */ event_base_dispatch(base); printf("The End."); //close(listener); return 0; } void do_accept(evutil_socket_t listener, short event, void *arg) { struct event_base *base = (struct event_base *)arg; evutil_socket_t fd; struct sockaddr_in sin; socklen_t slen = sizeof(sin); fd = accept(listener, (struct sockaddr *)&sin, &slen); if (fd < 0) { perror("accept"); return; } if (fd > FD_SETSIZE) { //这个if是参考了那个ROT13的例子，貌似是官方的疏漏，从select-based例子里抄过来忘了改 perror("fd > FD_SETSIZE\n"); return; } printf("ACCEPT: fd = %u\n", fd); //关联该sockfd，托管给event_base. BEV_OPT_CLOSE_ON_FREE--释放bufferevent时关闭底层传输端口。这将关闭底层套接字，释放底层bufferevent等。 struct bufferevent *bev = bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE); //设置读写对应的回调函数 bufferevent_setcb(bev, read_cb, NULL, error_cb, arg); //启用读写事件,其实是调用了event_add将相应读写事件加入事件监听队列poll. //如果相应事件不置为true，bufferevent是不会读写数据的 bufferevent_enable(bev, EV_READ|EV_PERSIST); // 进入bufferevent_setcb回调函数： // 在read_cb里面从input中读取数据，处理完毕后填充到output中； // write_cb对于服务端程序，只需要readcb就可以了，可以置为NULL； // error_cb用于处理一些错误信息 } void read_cb(struct bufferevent *bev, void *arg) { char line[MAX_LINE+1]; int n; //根据之前已经分配好的bufferevent 获取对应的连接描述符 evutil_socket_t fd = bufferevent_getfd(bev); while (n = bufferevent_read(bev, line, MAX_LINE), n > 0) { line[n] = '\0'; printf("fd=%u, Server gets the message from client read line: %s\n", fd, line); //直接将读取的结果,不做任何修改,直接返回给客户端 bufferevent_write(bev, line, n);//方案1 } } void write_cb(struct bufferevent *bev, void *arg) { printf("HelloWorld\n");//直接空代码即可，因为这里并不会被触发调用 } void error_cb(struct bufferevent *bev, short event, void *arg) { evutil_socket_t fd = bufferevent_getfd(bev); printf("fd = %u, ", fd); if (event & BEV_EVENT_TIMEOUT) { printf("Timed out\n"); //if bufferevent_set_timeouts() called } else if (event & BEV_EVENT_EOF) { printf("connection closed\n"); } else if (event & BEV_EVENT_ERROR) { printf("some other error\n"); } bufferevent_free(bev); }
客户端代码：
//客户端代码
//客户端代码
#include <stdio.h> #include <stdlib.h> #include <errno.h> #include <unistd.h> #include <string.h> #include <netinet/in.h> #include <sys/socket.h> #include <arpa/inet.h> #include <sys/types.h> #include <event2/event.h> #include <event2/bufferevent.h> #define SERV_PORT 9999 #define MAX_LINE 1024 void cmd_msg_cb(int fd, short event, void *arg); void read_cb(struct bufferevent *bev, void *arg); void error_cb(struct bufferevent *bev, short event, void *arg); int main(int argc, char *argv[]) { if(argc < 2) { perror("usage: echocli <IPadress>"); return 1; } evutil_socket_t sockfd; if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) { perror("socket\n"); return 1; } struct sockaddr_in servaddr; bzero(&servaddr, sizeof(servaddr)); servaddr.sin_family = AF_INET; servaddr.sin_port = htons(SERV_PORT); if(inet_pton(AF_INET, argv[1], &servaddr.sin_addr) < 1) { perror("inet_ntop\n"); return 1; } if(connect(sockfd, (struct sockaddr *) &servaddr, sizeof(servaddr)) < 0) { perror("connect\n"); return 1; } evutil_make_socket_nonblocking(sockfd); printf("Connect to server sucessfully!\n"); // build event base struct event_base *base = event_base_new(); if(base == NULL) { perror("event_base\n"); return 1; } //获取通信模式：这里为epoll const char *eventMechanism = event_base_get_method(base); printf("Event mechanism used is %s\n", eventMechanism); printf("sockfd = %d\n", sockfd); //关联该连接描述符sockfd，托管给event_base. struct bufferevent *bev = bufferevent_socket_new(base, sockfd, BEV_OPT_CLOSE_ON_FREE); //声明事件 struct event *ev_cmd; //创建一个用于监听标准输入的事件ev_cmd ev_cmd = event_new(base, STDIN_FILENO, EV_READ | EV_PERSIST, cmd_msg_cb, (void *)bev); //添加到事件队列当中.相当于告诉处理IO的管家，当有我的事件到达时你发给我(调用cmd_msg_cb函数) event_add(ev_cmd, NULL); //设置读写对应的回调函数 bufferevent_setcb(bev, read_cb, NULL, error_cb, (void *)ev_cmd); //使用bufferevent_enable(bev, EV_READ|EV_PERSIST)来启用read事件 bufferevent_enable(bev, EV_READ | EV_PERSIST); event_base_dispatch(base); printf("The End."); return 0; } void cmd_msg_cb(int fd, short event, void *arg) { char msg[MAX_LINE]; int nread = read(fd, msg, sizeof(msg)); if(nread < 0) { perror("stdio read fail\n"); return; } struct bufferevent *bev = (struct bufferevent *)arg; bufferevent_write(bev, msg, nread); } void read_cb(struct bufferevent *bev, void *arg) { char line[MAX_LINE + 1]; int n; evutil_socket_t fd = bufferevent_getfd(bev); while((n = bufferevent_read(bev, line, MAX_LINE)) > 0) { line[n] = '\0'; printf("fd = %u, read from server: %s", fd, line); } } void error_cb(struct bufferevent *bev, short event, void *arg) { evutil_socket_t fd = bufferevent_getfd(bev); printf("fd = %u, ", fd); if(event & BEV_EVENT_TIMEOUT) printf("Time out.\n"); // if bufferevent_set_timeouts() is called else if(event & BEV_EVENT_EOF) printf("Connection closed.\n"); else if(event & BEV_EVENT_ERROR) printf("Some other error.\n"); bufferevent_free(bev); struct event *ev = (struct event *)arg; event_free(ev); }
一、
1、编译服务端代码：
g++ -o server server.cpp -I/usr/libevent/include -I/usr/libevent/include/event2 -levent
2、编译可客户端代码：
g++ -o client client.cpp -I/usr/libevent/include -I/usr/libevent/include/event2 -levent
程序编码注意事项：
编程编译一定要加上 -I/usr/libevent/include -I/usr/libevent/include/event2 -levent 否则会出现很多未定义和找不到一些头文件的错误
二、运行程序如果报错
server: error while loading shared libraries: libevent-2.1.so.4: cannot open shared object file: No such file or directory
则：
1、有可能是装了多个 libevent而导致server无法识别哪一个，解决方法就是卸载掉一个libevent
2、只安装了一个libevent，但是也报这个错，解决方法
32位系统下：ln -s /usr/libevent/lib/libevent-2.1.so.4 /usr/lib/
64位系统下：ln -s /usr/libevent/lib/libevent-2.1.so.4 /usr/lib64/
三、编译报错
/usr/bin/ld: cannot find -levent
collect2: ld 返回 1则：
需要在用户目录下的.bash_profile文件加上这一行代码
vi .bash_profile
export LIBRARY_PATH=/usr/libevent/lib
保存退出，然后是文件生效
source .bash_profile