epoll工作流程
首先，需要调用epoll_create创建epoll；
此后我们就可以进行socket/bind/listen；
然后调用epoll_ctl进行注册；
接下来，就可以通过一个while(1)循环调用epoll_wait来等待事件的发生；
然后循环查看接收到的事件并进行处理；
1）如果事件是sever的socketfd我们就要进行accept，并且把接收到client的socketfd加入到要监听的事件中；
2）如果在监听过程中，需要修改操作方式（读/写），可以调用epoll_ctl来重新修改；
3）如果监听到某一个客户端关闭，那么我就需要再次调用epoll_ctl把它从epoll监听事件中删除。
epoll的结构体
typedef union epoll_data {
void *ptr;
int fd;
uint32_t u32;
uint64_t u64;
} epoll_data_t;
struct epoll_event {
uint32_t events; /* Epoll events */
epoll_data_t data; /* User data variable */
};
#include <stdio.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/epoll.h>
#include <errno.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <unistd.h>
#define SERV_PORT 8802
int main()
{
int i,flag;
int sockfd,clntfd,newfd;
int epfd,nfds;
ssize_t n;
char buffer[1024];
int s = sizeof(struct sockaddr);
struct sockaddr_in serv_addr;
struct sockaddr_in clnt_addr;
//定义epoll数据结构
struct epoll_event ev,events[20];
epfd = epoll_create(256);
//创建socket,并初始化事件ev
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0) {
perror("socket error!
");
return -1;
}
ev.data.fd = sockfd;
ev.events = EPOLLIN|EPOLLET;
//注册epoll事件
flag = epoll_ctl(epfd, EPOLL_CTL_ADD, sockfd, &ev);
if (flag < 0) {
perror("epoll_ctl error!
");
return -1;
}
bzero(&serv_addr, sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(SERV_PORT);
serv_addr.sin_addr.s_addr = htonl( INADDR_ANY );
flag = bind(sockfd, (struct sockaddr*)&serv_addr, sizeof(struct sockaddr));
if (flag < 0) {
perror("bind error!
");
return -1;
}
printf("bind
");
flag = listen(sockfd, 20);
if (flag < 0) {
perror("listen error!
");
return -1;
}
printf("listen
");
//开始循环
while (1) {
//等待事件发生,返回请求数目
nfds = epoll_wait(epfd, events, 20, 500);
//一次处理请求
for (i = 0; i < nfds; ++i) {
if (events[i].data.fd == sockfd){
clntfd = accept(sockfd, (struct sockaddr*)&clnt_addr,(unsigned int*)&s);
if (clntfd < 0) {
perror("accept error");
continue;
}
printf("accept
");
char *str = inet_ntoa(clnt_addr.sin_addr);
printf("accepnt the client ip : %s
",str);
//设置文件标识符，设置操作属性：写操作
ev.data.fd = clntfd;
ev.events = EPOLLOUT | EPOLLET;
//向创建的的epoll进行注册写操作
epoll_ctl(epfd, EPOLL_CTL_ADD, clntfd, &ev);
} else if (events[i].events & EPOLLOUT) {
printf("EPOLLOUT
");
if ((newfd = events[i].data.fd) < 0)
continue;
bzero(buffer,sizeof(buffer));
strcpy(buffer,"welcome to myserver!
");
flag = send(newfd, buffer, 1024, 0);
if (flag < 0) {
perror("send error");
continue;
}
//修改操作为读操作
ev.data.fd = clntfd;
ev.events = EPOLLIN | EPOLLET;
epoll_ctl(epfd, EPOLL_CTL_MOD, newfd, &ev);
} else if (events[i].events & EPOLLIN) {
printf("EPOLLIN
");
bzero(buffer,sizeof(buffer));
if ((newfd = events[i].data.fd) < 0)
continue;
if ((n = read(newfd, buffer, 1024)) < 0) {
if (errno == ECONNRESET){
close(newfd);
events[i].data.fd = -1;
printf("errno ECONRESET!
");
} else {
perror("readbuffer error!
");
}
} else if (n == 0) {//表示客户端已经关闭
close(newfd);
events[i].data.fd = -1;
printf("n为0
");
}
if (buffer[0] != '0')
printf("have read: %s
", buffer);
}
}
}
close(sockfd);
return 0;
}
引自：https://www.bbsmax.com/A/l1dymR3Gde/
优化
#include <stdio.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/epoll.h>
#include <errno.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <unistd.h>
#define SERV_PORT 8802
#define MAX_EVENTS 20
int main()
{
int listen_fd = socket(AF_INET, SOCK_STREAM, 0); //若成功则返回非负描述符，若失败则返回-1，第一个参数指明协议族（IPv4或IPv6等）
if (listen_fd < 0) { //第二个参数指明套接字类型，字节流套接字（SOCK_STREAM）和数据报套接字(SOCK_DGRAM)
perror("socket error!
");
return -1;
}
int epfd = epoll_create(256); //参数会被忽略，但是要大于0,
//若成功返回一个大于 0 的值，表示 epoll 实例；若返回 -1 表示出错
//针对监听的sockfd，创建epollevent
struct epoll_event event;
event.data.fd = listen_fd;
event.events = EPOLLIN | EPOLLET;
//注册epoll事件
int flag = epoll_ctl(epfd, EPOLL_CTL_ADD, listen_fd, &event); //int epoll_ctl(int epfd, int op, int fd, struct epoll_event *event);
if (flag < 0) { //成功返回0，出错返回-1
perror("epoll_ctl error!
");
return -1;
}
if (bindAndListenFd(listen_fd) < 0)
return -1;
//定义epoll数据结构
struct epoll_event events[MAX_EVENTS]; //可以使用vector，参见muduo源码中的使用
while (1) {
//等待事件发生,返回请求数目
int nfds = epoll_wait(epfd, events, MAX_EVENTS, 500); //maxevents: 返回的events的最大个数，如果最大个数大于实际触发的个数，则下次epoll_wait的时候仍然可以返回
//int epoll_wait(int epfd, struct epoll_event *events, int maxevents, int timeout);
//成功返回的是一个大于 0 的数，表示事件的个数；返回 0 表示的是超时时间到；若出错返回 -1.
for (int i = 0; i < nfds; ++i) {
if (events[i].data.fd == listen_fd) {
struct sockaddr_in client_addr;
int client_fd = accept(listen_fd, (struct sockaddr*)&client_addr, sizeof(client_addr)); //若成功则为非负描述符，若出错则返回-1
if (client_fd < 0) {
perror("accept error");
continue;
}
char *str = inet_ntoa(client_addr.sin_addr);
printf("accept the client ip : %s
",str);
onRecvNewConnect(epfd, client_fd);
} else if (events[i].events & EPOLLOUT) {
int sockfd = events[i].data.fd;
if (sockfd < 0)
continue;
onWriteFd(epfd, sockfd);
} else if (events[i].events & EPOLLIN) {
int sockfd = events[i].data.fd;
if (sockfd < 0)
continue;
if (onReadFd(epfd, sockfd) < 0) {
events[i].data.fd = -1;
}
}
}
}
close(sockfd);
return 0;
}
int bindAndListenFd(int sockfd) {
::fcntl(sockfd, F_SETFL, O_NONBLOCK); //设置非阻塞模式
struct sockaddr_in serv_addr;
bzero(&serv_addr, sizeof(serv_addr)); //void bzero(void *dest, size_t nbytes);
serv_addr.sin_family = AF_INET; //类似void *memset(void *dest, int c, size_t len);
serv_addr.sin_port = htons(SERV_PORT); //本地端口号转化为网络端口号 host to network short
serv_addr.sin_addr.s_addr = htonl(INADDR_ANY); //INADDR_ANY代表本机所有的IP地址 host to network long
int flag = bind(sockfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr)); //成功返回0，出错返回-1
if (flag < 0) {
perror("bind error!
");
return -1;
}
flag = listen(sockfd, 20); //成功返回0，出错返回-1
if (flag < 0) {
perror("listen error!
");
return -1;
}
return 0;
}
void onRecvNewConnect(int epfd, int clientfd) {
::fcntl(sockfd, F_SETFL, O_NONBLOCK); //设置非阻塞模式
//设置文件标识符，设置操作属性：写操作
struct epoll_event ev_client;
ev_client.data.fd = clintfd;
ev_client.events = EPOLLOUT | EPOLLET;
//向创建的的epoll进行注册写操作
epoll_ctl(epfd, EPOLL_CTL_ADD, clientfd, &ev_client);
}
void onWriteFd(int epfd, int sockfd) {
char buffer[1024];
bzero(buffer, sizeof(buffer));
strcpy(buffer, "welcome to myserver!
");
int flag = send(sockfd, buffer, 1024, 0);
if (flag < 0) {
perror("send error");
return;
}
//修改操作为读操作
struct epoll_event ev_client;
ev_client.data.fd = sockfd;
ev_client.events = EPOLLIN | EPOLLET;
epoll_ctl(epfd, EPOLL_CTL_MOD, sockfd, &ev_client);
}
int onReadFd(int epfd, int sockfd) {
char buffer[1024];
bzero(buffer, sizeof(buffer));
int n = read(sockfd, buffer, 1024);
if (n < 0) {
if (errno == ECONNRESET) {
close(sockfd);
printf("errno ECONRESET!
");
return -1;
} else {
perror("readbuffer error!
");
}
} else if (n == 0) { //表示客户端已经关闭
close(sockfd);
printf("n为0
");
return -1;
}
if (buffer[0] != '0')
printf("have read: %s
", buffer);
return 0;
}