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京东企业官网,网站优化服务,vps网站目录权限设置,做返利网站怎麼1：Epoll事件有两种模型： ET: (边沿触发) 》缓冲区状态发生变化时，触发一次 LT:(水平触发) 》有数据可读，读事件一直触发有空间可写，写事件一直触发。使用时，不指定事件模型，则默认是…

1：Epoll事件有两种模型：

ET: (边沿触发) ==》缓冲区状态发生变化时，触发一次

LT:(水平触发) ==》有数据可读，读事件一直触发有空间可写，写事件一直触发。

使用时，不指定事件模型，则默认是水平触发。

2：ET模型

ET边缘触发模型，涉及以下问题：

1：ET模式下，accept如果多个客户端同时触发，只返回一次的话，有丢失。

==》处理应该用while循环，一次性处理完。

if(epoll_events[i].data.fd == sockfd)
{//因为是et模式，所以这里要用whilestruct sockaddr_in client_addr;socklen_t client_len = sizeof(client_addr);while((connfd = accept(sockfd, (struct sockaddr*)&client_addr, &client_len))>=0){int oldSocketFlag = fcntl(connfd, F_GETFL, 0);int newSocketFlag = oldSocketFlag | O_NONBLOCK;if (fcntl(connfd, F_SETFD, newSocketFlag) == -1){close(connfd);printf("fcntl set nonblock error. fd [%d] \n", connfd);continue;}{struct epoll_event client_fd_event;client_fd_event.data.fd = connfd;client_fd_event.events = EPOLLIN | EPOLLOUT;client_fd_event.events |= EPOLLET; //ETif(epoll_ctl(epfd, EPOLL_CTL_ADD, connfd, &client_fd_event) == -1){printf("add clientfd to epoll error \n");close(connfd);continue;}printf("new client accept, client fd is %d. \n",connfd);}}
}

2: ET模式下，如果大量数据同时到达，只触发一次，取一次可能有数据丢失。应该用while循环一次取完。

if (events[i].events & EPOLLIN) 
{n = 0;// 一直读直到返回0或者 errno = EAGAINwhile ((nread = read(fd, buf + n, BUFSIZ-1)) > 0) {n += nread;}if (nread == -1 && errno != EAGAIN) {perror("read error");}ev.data.fd = fd;ev.events = events[i].events | EPOLLOUT;epoll_ctl(epfd, EPOLL_CTL_MOD, fd, &ev);
}

如果是可写，这里应该根据业务逻辑做一定的处理：

ssize_t socket_write(int sockfd, const char* buffer, size_t buflen)
{ssize_t tmp;size_t total = buflen;const char* p = buffer;while(1){tmp = write(sockfd, p, total);if(tmp < 0){// 当send收到信号时,可以继续写,但这里返回-1.if(errno == EINTR)return -1;// 当socket是非阻塞时,如返回此错误,表示写缓冲队列已满,// 在这里做延时后再重试.if(errno == EAGAIN){usleep(1000);continue;}return -1;}if((size_t)tmp == total)return buflen;total -= tmp;p += tmp;}return tmp;//返回已写字节数
}

3: LT模型

默认情况下，epoll模型为LT模型，如果有数据，会一直触发。

LT模型相对来说代码实现简单，但是cpu执行效率相对ET较差。

同时，LT模型，在accept和接受事件是不必担心的，但是可写事件会一直触发。

思考：可以把accept用LT模型，但是相关的连接fd用et模型。

同时，可读与可写的业务逻辑一般是可读，recv后，读完数据，更改事件为监听可写。

4：LT样例代码。

epoll_lt.c ==>会发现可写事件一直触发。

//业务逻辑可以优化，在读完后监听可写

//epoll默认时lt模式，
//lt模式有一直触发的问题，需要写完移除，或者读完移除//lt模式代码简单，可以根据业务读取固定的字节，直到读完为止/****************************************
默认就是lt模式： 水平触发需要处理，写完移除，读完移除https://cloud.tencent.com/developer/article/1636224
*****************************************/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>#include <fcntl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <sys/epoll.h>#define EPOLL_SIZE 1024
int main(int argc, char* argv[])
{int sockfd = socket(AF_INET, SOCK_STREAM, 0);if(sockfd <0){printf("create listen socket error \n");return -1;}//设置ip和端口可重用  设置非阻塞int on = 1;setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, (char*)&on, sizeof(on));setsockopt(sockfd, SOL_SOCKET, SO_REUSEPORT, (char*)&on, sizeof(on));//设置非阻塞int oldSocketFlag = fcntl(sockfd, F_GETFL, 0);int newSocketFlag = oldSocketFlag | O_NONBLOCK;if (fcntl(sockfd, F_SETFL, newSocketFlag) == -1){close(sockfd);printf("set nonblock error. \n");return -1;}//初始化服务器struct sockaddr_in bind_addr;bind_addr.sin_family = AF_INET;bind_addr.sin_addr.s_addr = htonl(INADDR_ANY);bind_addr.sin_port = htons(6666);//绑定端口if(bind(sockfd, (struct sockaddr*)&bind_addr, sizeof(bind_addr)) < 0){printf("bind sockfd error \n");close(sockfd);return -1;}//启动监听if(listen(sockfd, SOMAXCONN) < 0)//内核内规定的最大连接数{printf("listen sockfd error \n");close(sockfd);return -1;}//创建epoll int epfd = epoll_create(1);if(epfd == -1){printf("create epoll fd error . \n");close(sockfd);return -1;}//设置相关参数，默认lt，添加fd到epoll中struct epoll_event listen_fd_event;listen_fd_event.data.fd = sockfd;listen_fd_event.events = EPOLLIN; //默认是LTif(epoll_ctl(epfd, EPOLL_CTL_ADD, sockfd, &listen_fd_event) == -1){printf("epoll ctl listen fd error. \n");close(sockfd);return -1;}//这里是主要的逻辑区struct epoll_event epoll_events[EPOLL_SIZE];int nready;while(1){nready = epoll_wait(epfd, epoll_events, EPOLL_SIZE, 1000);if(nready < 0) {if (errno == EINTR)// 信号被中断continue;printf("epoll_wait error. \n");break;}else if(nready == 0) // 超时，继续{continue;}//开始处理响应的事件，这里是LTfor(int i =0; i<nready; i++){if(epoll_events[i].events & EPOLLIN){//accept判断，默认是LTif(epoll_events[i].data.fd == sockfd){//accept接收  以及设置非阻塞，放入epoll中struct sockaddr_in client_addr;socklen_t client_len = sizeof(client_addr);int clientfd = accept(sockfd, (struct sockaddr*)&client_addr, &client_len);if(clientfd == -1){printf("accept error %s \n ", strerror(errno));continue;}//设置非阻塞int oldSocketFlag = fcntl(clientfd, F_GETFL, 0);int newSocketFlag = oldSocketFlag | O_NONBLOCK;if (fcntl(clientfd, F_SETFD, newSocketFlag) == -1){close(clientfd);printf("fcntl set nonblock error. fd [%d] \n", clientfd);continue;}//加入epoll 监听读和写事件{struct epoll_event client_fd_event;client_fd_event.data.fd = clientfd;client_fd_event.events = EPOLLIN | EPOLLOUT;if(epoll_ctl(epfd, EPOLL_CTL_ADD, clientfd, &client_fd_event) == -1){printf("add clientfd to epoll error \n");close(clientfd);continue;}printf("new client accept, client fd is %d. \n",clientfd);}}else{printf("clinetfd [%d], recv data :\n", epoll_events[i].data.fd);//连接的客户发来数据char  recvbuff[1024] = {0};int recvsize = recv(epoll_events[i].data.fd, recvbuff, 1024, 0);if(recvsize == 0)// 关闭连接{if(epoll_ctl(epfd, EPOLL_CTL_DEL, epoll_events[i].data.fd, 0) == -1){printf("client disconnection error from epoll \n");close(epoll_events[i].data.fd);continue;}printf("client disconnected,clientfd is [%d] \n", epoll_events[i].data.fd);close(epoll_events[i].data.fd);}else if(recvsize < 0) //出错情况下也是移除{if (errno == EWOULDBLOCK && errno == EINTR) //不做处理{continue;}if(epoll_ctl(epfd, EPOLL_CTL_DEL, epoll_events[i].data.fd, 0) == -1){printf("recv client data error.del epoll error \n");close(epoll_events[i].data.fd);continue;}printf("recv client data error, clientfd is [%d] \n", epoll_events[i].data.fd);close(epoll_events[i].data.fd);}else{//正常接收到的数据printf("recv client[%d] data success [%s]. \n", epoll_events[i].data.fd, recvbuff);}}}else if(epoll_events[i].events & EPOLLOUT){if(epoll_events[i].data.fd == sockfd){continue;}//只处理客户端的连接 会一直触发//还需要接受 没法删除，这应该适合接收后发送的逻辑printf("EPOLLOUT send buff. \n");}else if(epoll_events[i].events & EPOLLERR) //给已经关闭的端口{//应该关闭移除该端口if(epoll_ctl(epfd, EPOLL_CTL_DEL, epoll_events[i].data.fd, 0) == -1){printf("recv client data error.del epoll error \n");close(epoll_events[i].data.fd);continue;}printf("epoll error . EPOLLERR \n");close(epoll_events[i].data.fd);}}}close(sockfd);close(epfd);return 0;
}

5：ET样例代码

/*************************************************
使用et,一定要设置成非阻塞1：处理accept2：处理发送和接受，发送
**************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>#include <fcntl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <sys/epoll.h>#define EPOLL_SIZE 1024
int main(int argc, char* argv[])
{int sockfd = socket(AF_INET, SOCK_STREAM, 0);if(sockfd <0){printf("create listen socket error \n");return -1;}//设置ip和端口可重用  设置非阻塞int on = 1;setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, (char*)&on, sizeof(on));setsockopt(sockfd, SOL_SOCKET, SO_REUSEPORT, (char*)&on, sizeof(on));//设置非阻塞int oldSocketFlag = fcntl(sockfd, F_GETFL, 0);int newSocketFlag = oldSocketFlag | O_NONBLOCK;if (fcntl(sockfd, F_SETFL, newSocketFlag) == -1){close(sockfd);printf("set nonblock error. \n");return -1;}//初始化服务器struct sockaddr_in bind_addr;bind_addr.sin_family = AF_INET;bind_addr.sin_addr.s_addr = htonl(INADDR_ANY);bind_addr.sin_port = htons(6666);//绑定端口if(bind(sockfd, (struct sockaddr*)&bind_addr, sizeof(bind_addr)) < 0){printf("bind sockfd error \n");close(sockfd);return -1;}//启动监听if(listen(sockfd, SOMAXCONN) < 0)//内核内规定的最大连接数{printf("listen sockfd error \n");close(sockfd);return -1;}//创建epoll int epfd = epoll_create(1);if(epfd == -1){printf("create epoll fd error . \n");close(sockfd);return -1;}//设置相关参数，默认lt，添加fd到epoll中//这里用的是ETstruct epoll_event listen_fd_event;listen_fd_event.data.fd = sockfd;listen_fd_event.events = EPOLLIN;listen_fd_event.events |= EPOLLET; //ETif(epoll_ctl(epfd, EPOLL_CTL_ADD, sockfd, &listen_fd_event) == -1){printf("epoll ctl listen fd error. \n");close(sockfd);return -1;}//ET模式下的处理，一定要是非阻塞的。//et模式处理时  要进行循环达到一次接受完，阻塞的话最后一次就会阻塞住struct epoll_event epoll_events[EPOLL_SIZE];int nready;while(1){nready = epoll_wait(epfd, epoll_events, EPOLL_SIZE, 1000);if(nready < 0) {if (errno == EINTR)// 信号被中断continue;printf("epoll_wait error. \n");break;}else if(nready == 0) // 超时，继续{continue;}int connfd = -1;for(int i =0; i<nready; i++){if(epoll_events[i].events & EPOLLIN) //有可读事件{if(epoll_events[i].data.fd == sockfd){//因为是et模式，所以这里要用whilestruct sockaddr_in client_addr;socklen_t client_len = sizeof(client_addr);while((connfd = accept(sockfd, (struct sockaddr*)&client_addr, &client_len))>=0){int oldSocketFlag = fcntl(connfd, F_GETFL, 0);int newSocketFlag = oldSocketFlag | O_NONBLOCK;if (fcntl(connfd, F_SETFD, newSocketFlag) == -1){close(connfd);printf("fcntl set nonblock error. fd [%d] \n", connfd);continue;}{struct epoll_event client_fd_event;client_fd_event.data.fd = connfd;client_fd_event.events = EPOLLIN | EPOLLOUT;client_fd_event.events |= EPOLLET; //ETif(epoll_ctl(epfd, EPOLL_CTL_ADD, connfd, &client_fd_event) == -1){printf("add clientfd to epoll error \n");close(connfd);continue;}printf("new client accept, client fd is %d. \n",connfd);}}}else{printf("clinetfd [%d], recv data :\n", epoll_events[i].data.fd);//开始接受char  recvbuff[1024] = {0};int recvsize = -1;//一次性读完while((recvsize = recv(epoll_events[i].data.fd, recvbuff, 1024, 0))>0){printf("recvbuff:[%s] recvsize:[%d] \n", recvbuff, recvsize);}if(recvsize == 0){if(epoll_ctl(epfd, EPOLL_CTL_DEL, epoll_events[i].data.fd, 0) == -1){printf("client disconnection error from epoll \n");close(epoll_events[i].data.fd);continue;}printf("client disconnected,clientfd is [%d] \n", epoll_events[i].data.fd);close(epoll_events[i].data.fd);}else if(recvsize < 0){if (errno == EWOULDBLOCK && errno == EINTR) //不做处理{continue;}if(epoll_ctl(epfd, EPOLL_CTL_DEL, epoll_events[i].data.fd, 0) == -1){printf("recv client data error.del epoll error \n");close(epoll_events[i].data.fd);continue;}printf("recv client data error, clientfd is [%d] \n", epoll_events[i].data.fd);close(epoll_events[i].data.fd);}}}else if(epoll_events[i].events & EPOLLOUT){if(epoll_events[i].data.fd == sockfd){continue;}//这里et，应该只触发一次printf("EPOLLOUT send buff\n ");}else if(epoll_events[i].events & EPOLLERR) //给已经关闭的端口{//应该关闭移除该端口if(epoll_ctl(epfd, EPOLL_CTL_DEL, epoll_events[i].data.fd, 0) == -1){printf("recv client data error.del epoll error \n");close(epoll_events[i].data.fd);continue;}printf("epoll error . EPOLLERR \n");close(epoll_events[i].data.fd);}}}close(sockfd);close(epfd);return 0;
}