epoll 示例代碼 · 音視頻/C++/k8s/Docker等等學習筆記

[TOC] ## Epoll工作方式 ***** `LT`水平觸發 >LT(level triggered)是epoll缺省的工作方式，并且同時支持block和no-block socket.在這種做法中，內核告訴你一個文件描述符是否就緒了，然后你可以對這個就緒的fd進行IO操作。如果你不作任何操作，內核還是會繼續通知你?的，所以，這種模式編程出錯誤可能性要小一點。傳統的select/poll都是這種模型的代表． `ET`邊緣觸發 >ET (edge-triggered)是高速工作方式，只支持no-block socket，它效率要比LT更高。ET與LT的區別在于，當一個新的事件到來時，ET模式下當然可以從epoll_wait調用中獲取到這個事件，可是如果這次沒有把這個事件對應的套接字緩沖區處理完，在這個套接字中沒有新的事件再次到來時，在ET模式下是無法再次從epoll_wait調用中獲取這個事件的。而LT模式正好相反，只要一個事件對應的套接字緩沖區還有數據，就總能從epoll_wait中獲取這個事件。 ## 服務端 server.cpp ``` #include <stdio.h> #include <stdlib.h> #include <string.h> #include <errno.h> #include <netinet/in.h> #include <sys/socket.h> #include <arpa/inet.h> #include <sys/epoll.h> #include <unistd.h> #include <sys/types.h> #define IPADDRESS "127.0.0.1" #define PORT 8787 #define MAXSIZE 1024 #define LISTENQ 5 #define FDSIZE 1000 #define EPOLLEVENTS 100 //函數聲明 //創建套接字并進行綁定 static int socket_bind(const char* ip,int port); //IO多路復用epoll static void do_epoll(int listenfd); //事件處理函數 static void handle_events(int epollfd,struct epoll_event *events,int num,int listenfd,char *buf); //處理接收到的連接 static void handle_accpet(int epollfd,int listenfd); //讀處理 static void do_read(int epollfd,int fd,char *buf); //寫處理 static void do_write(int epollfd,int fd,char *buf); //添加事件 static void add_event(int epollfd,int fd,int state); //修改事件 static void modify_event(int epollfd,int fd,int state); //刪除事件 static void delete_event(int epollfd,int fd,int state); int main(int argc,char *argv[]) { int listenfd; listenfd = socket_bind(IPADDRESS,PORT); listen(listenfd,LISTENQ); do_epoll(listenfd); return 0; } static int socket_bind(const char* ip,int port) { int listenfd; struct sockaddr_in servaddr; listenfd = socket(AF_INET,SOCK_STREAM,0); if (listenfd == -1) { perror("socket error:"); exit(1); } bzero(&servaddr,sizeof(servaddr)); servaddr.sin_family = AF_INET; inet_pton(AF_INET,ip,&servaddr.sin_addr); servaddr.sin_port = htons(port); if (bind(listenfd,(struct sockaddr*)&servaddr,sizeof(servaddr)) == -1) { perror("bind error: "); exit(1); } return listenfd; } static void do_epoll(int listenfd) { int epollfd; struct epoll_event events[EPOLLEVENTS]; int ret; char buf[MAXSIZE]; memset(buf,0,MAXSIZE); //創建一個描述符 epollfd = epoll_create(FDSIZE); //添加監聽描述符事件 add_event(epollfd,listenfd,EPOLLIN); for ( ; ; ) { //獲取已經準備好的描述符事件 ret = epoll_wait(epollfd,events,EPOLLEVENTS,-1); handle_events(epollfd,events,ret,listenfd,buf); } close(epollfd); } static void handle_events(int epollfd,struct epoll_event *events,int num,int listenfd,char *buf) { int i; int fd; //進行選好遍歷 for (i = 0;i < num;i++) { fd = events[i].data.fd; //根據描述符的類型和事件類型進行處理 if ((fd == listenfd) &&(events[i].events & EPOLLIN)) handle_accpet(epollfd,listenfd); else if (events[i].events & EPOLLIN) do_read(epollfd,fd,buf); else if (events[i].events & EPOLLOUT) do_write(epollfd,fd,buf); } } static void handle_accpet(int epollfd,int listenfd) { int clifd; struct sockaddr_in cliaddr; socklen_t cliaddrlen; clifd = accept(listenfd,(struct sockaddr*)&cliaddr,&cliaddrlen); if (clifd == -1) perror("accpet error:"); else { printf("accept a new client: %s:%d\n",inet_ntoa(cliaddr.sin_addr),cliaddr.sin_port); //添加一個客戶描述符和事件 add_event(epollfd,clifd,EPOLLIN); } } static void do_read(int epollfd,int fd,char *buf) { int nread; nread = read(fd,buf,MAXSIZE); if (nread == -1) { perror("read error:"); close(fd); delete_event(epollfd,fd,EPOLLIN); } else if (nread == 0) { fprintf(stderr,"client close.\n"); close(fd); delete_event(epollfd,fd,EPOLLIN); } else { printf("read message is : %s",buf); //修改描述符對應的事件，由讀改為寫 modify_event(epollfd,fd,EPOLLOUT); } } static void do_write(int epollfd,int fd,char *buf) { int nwrite; nwrite = write(fd,buf,strlen(buf)); if (nwrite == -1) { perror("write error:"); close(fd); delete_event(epollfd,fd,EPOLLOUT); } else modify_event(epollfd,fd,EPOLLIN); memset(buf,0,MAXSIZE); } static void add_event(int epollfd,int fd,int state) { struct epoll_event ev; ev.events = state; ev.data.fd = fd; ev.events = EPOLLIN | EPOLLET; //讀入邊緣觸發 epoll_ctl(epollfd,EPOLL_CTL_ADD,fd,&ev); } static void delete_event(int epollfd,int fd,int state) { struct epoll_event ev; ev.events = state; ev.data.fd = fd; epoll_ctl(epollfd,EPOLL_CTL_DEL,fd,&ev); } static void modify_event(int epollfd,int fd,int state) { struct epoll_event ev; ev.events = state; ev.data.fd = fd; epoll_ctl(epollfd,EPOLL_CTL_MOD,fd,&ev); } ``` ## 客戶端 ``` #include <netinet/in.h> #include <sys/socket.h> #include <stdio.h> #include <string.h> #include <stdlib.h> #include <sys/epoll.h> #include <time.h> #include <unistd.h> #include <sys/types.h> #include <arpa/inet.h> #define MAXSIZE 1024 #define IPADDRESS "192.168.0.212" #define SERV_PORT 8787 #define FDSIZE 1024 #define EPOLLEVENTS 20 static void handle_connection(int sockfd); static void handle_events(int epollfd,struct epoll_event *events,int num,int sockfd,char *buf); static void do_read(int epollfd,int fd,int sockfd,char *buf); static void do_write(int epollfd,int fd,int sockfd,char *buf); static void add_event(int epollfd,int fd,int state); static void delete_event(int epollfd,int fd,int state); static void modify_event(int epollfd,int fd,int state); int main(int argc,char *argv[]) { int sockfd; struct sockaddr_in servaddr; sockfd = socket(AF_INET,SOCK_STREAM,0); bzero(&servaddr,sizeof(servaddr)); servaddr.sin_family = AF_INET; servaddr.sin_port = htons(SERV_PORT); inet_pton(AF_INET,IPADDRESS,&servaddr.sin_addr); connect(sockfd,(struct sockaddr*)&servaddr,sizeof(servaddr)); //處理連接 handle_connection(sockfd); close(sockfd); return 0; } static void handle_connection(int sockfd) { int epollfd; struct epoll_event events[EPOLLEVENTS]; char buf[MAXSIZE]; int ret; epollfd = epoll_create(FDSIZE); add_event(epollfd,STDIN_FILENO,EPOLLIN); for ( ; ; ) { ret = epoll_wait(epollfd,events,EPOLLEVENTS,-1); handle_events(epollfd,events,ret,sockfd,buf); } close(epollfd); } static void handle_events(int epollfd,struct epoll_event *events,int num,int sockfd,char *buf) { int fd; int i; for (i = 0;i < num;i++) { fd = events[i].data.fd; if (events[i].events & EPOLLIN) do_read(epollfd,fd,sockfd,buf); else if (events[i].events & EPOLLOUT) do_write(epollfd,fd,sockfd,buf); } } static void do_read(int epollfd,int fd,int sockfd,char *buf) { int nread; nread = read(fd,buf,MAXSIZE); if (nread == -1) { perror("read error:"); close(fd); } else if (nread == 0) { fprintf(stderr,"server close.\n"); close(fd); } else { if (fd == STDIN_FILENO) add_event(epollfd,sockfd,EPOLLOUT); else { delete_event(epollfd,sockfd,EPOLLIN); add_event(epollfd,STDOUT_FILENO,EPOLLOUT); } } } static void do_write(int epollfd,int fd,int sockfd,char *buf) { int nwrite; nwrite = write(fd,buf,strlen(buf)); if (nwrite == -1) { perror("write error:"); close(fd); } else { if (fd == STDOUT_FILENO) delete_event(epollfd,fd,EPOLLOUT); else modify_event(epollfd,fd,EPOLLIN); } memset(buf,0,MAXSIZE); } static void add_event(int epollfd,int fd,int state) { struct epoll_event ev; ev.events = state; ev.data.fd = fd; epoll_ctl(epollfd,EPOLL_CTL_ADD,fd,&ev); } static void delete_event(int epollfd,int fd,int state) { struct epoll_event ev; ev.events = state; ev.data.fd = fd; epoll_ctl(epollfd,EPOLL_CTL_DEL,fd,&ev); } static void modify_event(int epollfd,int fd,int state) { struct epoll_event ev; ev.events = state; ev.data.fd = fd; epoll_ctl(epollfd,EPOLL_CTL_MOD,fd,&ev); } ```