上篇我們講到epoll的函數和性能。這一篇用用這些個函數，給出一個最簡單的epoll的例子。

// // a simple echo server using epoll in linux // // 2009-11-05 // by sparkling // #include <sys/socket.h> #include <sys/epoll.h> #include <netinet/in.h> #include <arpa/inet.h> #include <fcntl.h> #include <unistd.h> #include <stdio.h> #include <errno.h> #include <iostream> using namespace std; #define MAX_EVENTS 500 struct myevent_s { int fd; void (*call_back)(int fd, int events, void *arg); int events; void *arg; int status; // 1: in epoll wait list, 0 not in char buff[128]; // recv data buffer int len; long last_active; // last active time }; // set event void EventSet(myevent_s *ev, int fd, void (*call_back)(int, int, void*), void *arg) { ev->fd = fd; ev->call_back = call_back; ev->events = 0; ev->arg = arg; ev->status = 0; ev->last_active = time(NULL); } // add/mod an event to epoll void EventAdd(int epollFd, int events, myevent_s *ev) { struct epoll_event epv = {0, {0}}; int op; epv.data.ptr = ev; epv.events = ev->events = events; if(ev->status == 1){ op = EPOLL_CTL_MOD; } else{ op = EPOLL_CTL_ADD; ev->status = 1; } if(epoll_ctl(epollFd, op, ev->fd, &epv) < 0) printf("Event Add failed[fd=%d]/n", ev->fd); else printf("Event Add OK[fd=%d]/n", ev->fd); } // delete an event from epoll void EventDel(int epollFd, myevent_s *ev) { struct epoll_event epv = {0, {0}}; if(ev->status != 1) return; epv.data.ptr = ev; ev->status = 0; epoll_ctl(epollFd, EPOLL_CTL_DEL, ev->fd, &epv); } int g_epollFd; myevent_s g_Events[MAX_EVENTS+1]; // g_Events[MAX_EVENTS] is used by listen fd void RecvData(int fd, int events, void *arg); void SendData(int fd, int events, void *arg); // accept new connections from clients void AcceptConn(int fd, int events, void *arg) { struct sockaddr_in sin; socklen_t len = sizeof(struct sockaddr_in); int nfd, i; // accept if((nfd = accept(fd, (struct sockaddr*)&sin, &len)) == -1) { if(errno != EAGAIN && errno != EINTR) { printf("%s: bad accept", __func__); } return; } do { for(i = 0; i < MAX_EVENTS; i++) { if(g_Events[i].status == 0) { break; } } if(i == MAX_EVENTS) { printf("%s:max connection limit[%d].", __func__, MAX_EVENTS); break; } // set nonblocking if(fcntl(nfd, F_SETFL, O_NONBLOCK) < 0) break; // add a read event for receive data EventSet(&g_Events[i], nfd, RecvData, &g_Events[i]); EventAdd(g_epollFd, EPOLLIN|EPOLLET, &g_Events[i]); printf("new conn[%s:%d][time:%d]/n", inet_ntoa(sin.sin_addr), ntohs(sin.sin_port), g_Events[i].last_active); }while(0); } // receive data void RecvData(int fd, int events, void *arg) { struct myevent_s *ev = (struct myevent_s*)arg; int len; // receive data len = recv(fd, ev->buff, sizeof(ev->buff)-1, 0); EventDel(g_epollFd, ev); if(len > 0) { ev->len = len; ev->buff[len] = '/0'; printf("C[%d]:%s/n", fd, ev->buff); // change to send event EventSet(ev, fd, SendData, ev); EventAdd(g_epollFd, EPOLLOUT|EPOLLET, ev); } else if(len == 0) { close(ev->fd); printf("[fd=%d] closed gracefully./n", fd); } else { close(ev->fd); printf("recv[fd=%d] error[%d]:%s/n", fd, errno, strerror(errno)); } } // send data void SendData(int fd, int events, void *arg) { struct myevent_s *ev = (struct myevent_s*)arg; int len; // send data len = send(fd, ev->buff, ev->len, 0); ev->len = 0; EventDel(g_epollFd, ev); if(len > 0) { // change to receive event EventSet(ev, fd, RecvData, ev); EventAdd(g_epollFd, EPOLLIN|EPOLLET, ev); } else { close(ev->fd); printf("recv[fd=%d] error[%d]/n", fd, errno); } } void InitListenSocket(int epollFd, short port) { int listenFd = socket(AF_INET, SOCK_STREAM, 0); fcntl(listenFd, F_SETFL, O_NONBLOCK); // set non-blocking printf("server listen fd=%d/n", listenFd); EventSet(&g_Events[MAX_EVENTS], listenFd, AcceptConn, &g_Events[MAX_EVENTS]); // add listen socket EventAdd(epollFd, EPOLLIN|EPOLLET, &g_Events[MAX_EVENTS]); // bind & listen sockaddr_in sin; bzero(&sin, sizeof(sin)); sin.sin_family = AF_INET; sin.sin_addr.s_addr = INADDR_ANY; sin.sin_port = htons(port); bind(listenFd, (const sockaddr*)&sin, sizeof(sin)); listen(listenFd, 5); } int main(int argc, char **argv) { short port = 12345; // default port if(argc == 2){ port = atoi(argv[1]); } // create epoll g_epollFd = epoll_create(MAX_EVENTS); if(g_epollFd <= 0) printf("create epoll failed.%d/n", g_epollFd); // create & bind listen socket, and add to epoll, set non-blocking InitListenSocket(g_epollFd, port); // event loop struct epoll_event events[MAX_EVENTS]; printf("server running:port[%d]/n", port); int checkPos = 0; while(1){ // a simple timeout check here, every time 100, better to use a mini-heap, and add timer event long now = time(NULL); for(int i = 0; i < 100; i++, checkPos++) // doesn't check listen fd { if(checkPos == MAX_EVENTS) checkPos = 0; // recycle if(g_Events[checkPos].status != 1) continue; long duration = now - g_Events[checkPos].last_active; if(duration >= 60) // 60s timeout { close(g_Events[checkPos].fd); printf("[fd=%d] timeout[%d--%d]./n", g_Events[checkPos].fd, g_Events[checkPos].last_active, now); EventDel(g_epollFd, &g_Events[checkPos]); } } // wait for events to happen int fds = epoll_wait(g_epollFd, events, MAX_EVENTS, 1000); if(fds < 0){ printf("epoll_wait error, exit/n"); break; } for(int i = 0; i < fds; i++){ myevent_s *ev = (struct myevent_s*)events[i].data.ptr; if((events[i].events&EPOLLIN)&&(ev->events&EPOLLIN)) // read event { ev->call_back(ev->fd, events[i].events, ev->arg); } if((events[i].events&EPOLLOUT)&&(ev->events&EPOLLOUT)) // write event { ev->call_back(ev->fd, events[i].events, ev->arg); } } } // free resource return 0; }

上面是一個echo server的例子，下來我們看下echo client的例子

#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <errno.h> #include <string.h> #include <netdb.h> #include <sys/types.h> #include <netinet/in.h> #include <sys/socket.h>#define MAXDATASIZE 100 // max number of bytes we can get at onceint main(int argc, char *argv[]) {int sockfd, numbytes;char buf[MAXDATASIZE];struct hostent *he;struct sockaddr_in their_addr; // connector'saddress informationif (( argc == 1) || (argc==2) ) {fprintf(stderr,"usage: client hostname\nEx:\n$./client01 ip port\n");exit(1);}if ((he=gethostbyname(argv[1])) == NULL) { // get the host infoherror("gethostbyname");exit(1);}if ((sockfd = socket(PF_INET, SOCK_STREAM, 0)) == -1) {perror("socket");exit(1);}their_addr.sin_family = AF_INET; // host byte ordertheir_addr.sin_port = htons(atoi(argv[2])); // short, network byte ordertheir_addr.sin_addr = *((struct in_addr *)he->h_addr);memset(their_addr.sin_zero, '', sizeof their_addr.sin_zero);if (connect(sockfd, (struct sockaddr *)&their_addr, sizeof their_addr) == -1) {perror("connect");exit(1);}while( 1 ){if(send(sockfd, "hello, this is client message!", strlen("hello, this is client message!"), 0 ) == -1){perror("send");}if ((numbytes=recv(sockfd, buf, MAXDATASIZE-1, 0)) == -1){perror("recv");}else if( numbytes == 0 ){printf("Remote server has shutdown!\n");break;}buf[numbytes] = '';printf("Received: %s \n",buf);sleep(1);}close(sockfd);return 0; }

以上客戶端和服務器例子均來自網絡，自己沒有單獨寫，因為覺得自己寫了跟著個差不多還浪費時間，大家有興趣可以去研究下libevent和libev，這都是很好用的C風格的epoll網絡庫，或者之際看ASIO吧。

轉載請注明：C++愛好者博客???淺析epoll – epoll例子以及分析

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