Undefined

Epoll

2018/06/27

1.分析

STDIN_FILENO：接收键盘的输入

STDOUT_FILENO：向屏幕输出

epoll步骤

参考：IO多路复用之epoll总结 https://www.cnblogs.com/Anker/p/3263780.html

#include <sys/epoll.h>
int epoll_create(int size);
int epoll_ctl(int epfd, int op, int fd, struct epoll_event *event);
int epoll_wait(int epfd, struct epoll_event * events, int maxevents, int timeout);

  • 调用epoll_create()建立一个epoll对象(在epoll文件系统中为这个句柄对象分配资源)

  • 调用epoll_ctl向epoll对象中添加这100万个连接的套接字

    EPOLL_CTL_ADD：注册新的fd到epfd中； EPOLL_CTL_MOD：修改已经注册的fd的监听事件； EPOLL_CTL_DEL：从epfd中删除一个fd；

  • 调用epoll_wait收集发生的事件的连接

关于ET、LT两种工作模式

LT：水平触发，效率会低于ET触发，尤其在大并发，大流量的情况下。但是LT对代码编写要求比较低，不容易出现问题。LT模式服务编写上的表现是：只要有数据没有被获取，内核就不断通知你，因此不用担心事件丢失的情况。

ET：边缘触发，效率非常高，在并发，大流量的情况下，会比LT少很多epoll的系统调用，因此效率高。但是对编程要求高，需要细致的处理每个请求，否则容易发生丢失事件的情况。

ev.events = EPOLLIN; //，默认LT模式
ev.events = EPOLLIN | EPOLLET;  表示ET模式

2.服务端代码

#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 6666
#define MAXSIZE 1024
#define LISTENQ 5 
#define FDSIZE 1000
#define EPOLLEVENTS 100

int socket_bind(const char*ip, int port);
void  do_epoll(int listenfd );
void handle_events(int epollfd ,struct epoll_event* events ,int num ,int listenfd ,char*buf);
void handle_accpet(int epolled ,int listenfd);
void do_read(int epolled , int fd ,char* buf);
void do_write(int epolled ,int fd ,char *buf);
void add_event(int epolled ,int fd, int state );
void modify_event(int epolled ,int fd ,int state );
void delete_event(int epolled ,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 ;
}

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;
}

void do_epoll(int listenfd){
	int epollfd;
	struct epoll_event events[EPOLLEVENTS];
	int ret;
	char buf[MAXSIZE];
	memset(buf,0,sizeof(buf));

	epollfd = epoll_create(FDSIZE);

	add_event(epollfd, listenfd, EPOLLIN);

	while(1){
		ret = epoll_wait(epollfd ,events ,EPOLLEVENTS ,-1);
		handle_events(epollfd, events ,ret ,listenfd, buf);
	}
	close(epollfd);
}

void handle_events(int epollfd, struct epoll_event *events ,int nums, int listenfd, char*buf){
	int i , fd ;

	for (i = 0 ; i < nums; i++){
		fd = events[i].data.fd;
		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);
	}
}

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);
		add_event(epollfd ,clifd ,EPOLLIN);
	}
}

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);
		modify_event(epollfd, fd ,EPOLLOUT);
	}
}

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);
}

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);
}

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);
}

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);
}

3.客户端代码

#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  "127.0.0.1"
#define SERV_PORT 6666
#define FDSIZE 1024
#define EPOLLEVENTS 20

void handle_connection(int sockfd);
void handle_events(int epollfd ,struct epoll_event *events,int num ,int sockfd ,char*buf);
void do_read(int epollfd , int fd ,int sockfd, char* buf);
void do_write(int epollfd ,int fd ,int sockfd ,char* buf);
void add_event(int epollfd ,int fd ,int state );
void delete_event(int epollfd, int fd ,int state );
void modify_event(int epollfd ,int fd ,int state );
int count = 0 ;

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);
	if ( 0 !=  connect(sockfd, (struct sockaddr*)&servaddr ,sizeof(servaddr)) ){
		printf("connect %s-%d faild \n", IPADDRESS, SERV_PORT);
		close (sockfd);
		return -1;
	}
	handle_connection(sockfd);
	close(sockfd);
	return 0 ;
}

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);
	while(1){
		ret = epoll_wait(epollfd, events ,EPOLLEVENTS ,-1);
		handle_events(epollfd ,events ,ret, sockfd ,buf);
	}
	close(epollfd);
}


void handle_events(int epollfd ,struct epoll_event *events ,int num ,int sockfd, char*buf){
	int fd ,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);
	}
}

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) // STDIN_FILENO：接收键盘的输入
			add_event(epollfd ,sockfd ,EPOLLOUT);
		else{ //从服务器读来的数据 删除读，打开写
			delete_event(epollfd, sockfd ,EPOLLIN);
			add_event(epollfd ,STDOUT_FILENO, EPOLLOUT); //往屏幕输出
		}
	}
}


void do_write(int epollfd ,int fd ,int sockfd ,char*buf){
	int nwrite ;
	char temp[100];
	buf[strlen(buf) -1 ] = '\0';
	snprintf(temp, sizeof(temp), "%s_%02d\n",buf ,count++);
	nwrite = write(fd ,temp ,strlen(temp));

	if(nwrite == -1 ){
		perror("write error: ");
		close(fd);
	}else{
		if( fd == STDOUT_FILENO)//STDOUT_FILENO：向屏幕输出
			delete_event(epollfd, fd ,EPOLLOUT);
		else
			modify_event(epollfd ,fd, EPOLLIN);
	}
	memset(buf, 0 ,sizeof(buf));
}

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);
}


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);

}

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);
}


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