Libevent使用例項1 (簡單)
阿新 • • 發佈：2018-12-11
客戶端：
#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; } //兩個引數依次是伺服器端的IP地址，埠號 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(); //監聽讀事件 struct event* ev_sockfd = event_new(base,sockfd,EV_READ | EV_PERSIST, socket_read_cb, NULL); event_add(ev_sockfd, NULL); //正式新增事件 //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); //回撥函式：引數是：fd,event,arg event_add(ev_cmd,NULL); //新增事件 event_base_dispatch(base); //進入迴圈，等待就緒事件並執行事件處理 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; //該回調函式作用是從標準輸入讀到msg,再把msg的資料傳送給sockfd(伺服器端) char msg[1024]; int ret = read(fd,msg,sizeof(msg)); //ret是讀取的長度 if(ret <= 0) { perror("read fail"); exit(1); } int sockfd = *((int*)arg); //把終端的訊息傳送給伺服器端 //為了簡單起見，不考慮寫一半資料的情況 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]; //為了簡單起見，不考慮寫一半資料的情況 int len = read(fd,msg,sizeof(msg)-1); if(len <= 0) { perror("read fail"); exit(1); } msg[len] = '\0'; printf("recv %s 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); //將IP地址轉換為網路位元組序整數 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); //設定成不阻塞 return sockfd; }
gcc -o primary_client primary_client.c -levent
伺服器端：
#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(); //新增監聽客戶端請求連線事件 struct event* ev_listen = event_new(base, listener, EV_READ | EV_PERSIST, accept_cb, base);//將base引數傳給回撥函式 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傳入的實參就是base，但是是void*,所以強制轉換回來 //僅僅是為了動態建立一個event結構體 struct event *ev = event_new(NULL, -1, 0, NULL, NULL); //將動態建立的結構體作為event的回撥引數 event_assign(ev, base, sockfd, EV_READ | EV_PERSIST, socket_read_cb, (void*)ev); //監聽讀事件 //event_assign等價於：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,監聽讀事件的回撥函式 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); //將msg字串複製到reply_msg的末尾 write(fd,reply_msg,strlen(reply_msg) ); //向客戶端傳送回覆已收到的資料 } 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; //允許多次繫結同一地址要用在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; //跨平臺同一介面，將套接字設定為非阻塞狀態 evutil_make_socket_nonblocking(listener); return listener; error: errno_save = errno; evutil_closesocket(listener); errno = errno_save; return -1; }
gcc -o primary_server.c primary_server -levent
注意：
編譯時要在編譯語句後面加上 -levent 表示要連結event靜態函式庫,如果沒有這一句,那麼整個連結將會出錯,類似與下面的結局：
main.cpp:(.text+0x2c)：對‘evutil_make_listen_socket_reuseable’未定義的引用 main.cpp:(.text+0xec)：對‘evutil_make_socket_nonblocking’未定義的引用 main.cpp:(.text+0xf1)：對‘event_base_new’未定義的引用 main.cpp:(.text+0x13f)：對‘event_new’未定義的引用 main.cpp:(.text+0x154)：對‘event_add’未定義的引用 main.cpp:(.text+0x160)：對‘event_base_dispatch’未定義的引用 main.cpp:(.text+0x16c)：對‘event_base_free’未定義的引用 /tmp/ccFk4bSL.o：在函式‘do_accept(int, short, void*)’中： main.cpp:(.text+0x22e)：對‘bufferevent_socket_new’未定義的引用 main.cpp:(.text+0x254)：對‘bufferevent_setcb’未定義的引用 main.cpp:(.text+0x265)：對‘bufferevent_enable’未定義的引用 /tmp/ccFk4bSL.o：在函式‘read_cb(bufferevent*, void*)’中： main.cpp:(.text+0x28f)：對‘bufferevent_getfd’未定義的引用 main.cpp:(.text+0x2f5)：對‘bufferevent_write’未定義的引用 main.cpp:(.text+0x313)：對‘bufferevent_read’未定義的引用 /tmp/ccFk4bSL.o：在函式‘error_cb(bufferevent*, short, void*)’中： main.cpp:(.text+0x357)：對‘bufferevent_getfd’未定義的引用 main.cpp:(.text+0x408)：對‘bufferevent_free’未定義的引用
執行結果:
客戶端：
伺服器：
