epoll中ET和LT模式的区别

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <assert.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sys/epoll.h>
#include <pthread.h>

/*宏定义区*/
#define MAX_EVENT_NUMBER 1024
#define BUFFER_SIZE 10

int setnonblocking(int fd)
{
int old_option = fcntl(fd,F_GETFL);
int new_option = old_option | O_NONBLOCK;
fcntl(fd,F_SETFL,new_option);
return old_option;
}

void addfd(int epollfd,int fd,bool enable_et)
{
epoll_event event;
event.data.fd = fd;
event.events = EPOLLIN;

if(enable_et)
{
event.events |= EPOLLET;
}

epoll_ctl(epollfd,EPOLL_CTL_ADD,fd,&event);
setnonblocking(fd);
}

void lt(epoll_event* events,int number,int epollfd,int listenfd)
{
char buf[BUFFER_SIZE];
for(int i = 0;i<number;i++)
{
int sockfd = events[i].data.fd;
if(sockfd == listenfd)
{
struct sockaddr_in client_address;
socklen_t client_addrlen = sizeof(sockaddr_in);

int connfd = accept(listenfd,(struct sockaddr*)&client_address,&client_addrlen);

//将fd加入到epoll的内核事件表中
addfd(epollfd,connfd,false);
}
else if(events[i].events & EPOLLIN)
{
//只要socket读缓存中还有未读取的数据,这段代码就会一直被触发
printf("event trigger once\r\n");
memset(buf,0,BUFFER_SIZE);
int ret = recv(sockfd,buf,BUFFER_SIZE,0);
if(ret < 0)
{
close(sockfd);
continue;
}
printf("get %d bytes of content: %s\r\n",ret,buf);
}
else
{
printf("something else happened\r\n");
}
}
}

/*et工作模式*/
void et(epoll_event* events,int number,int epollfd,int listenfd)
{
char buf[BUFFER_SIZE];
for(int i = 0;i<number;i++)
{
int sockfd = events[i].data.fd;
if(sockfd == listenfd)
{
struct sockaddr_in client_address;
socklen_t client_addrlen = sizeof(sockaddr_in);

int connfd = accept(listenfd,(struct sockaddr*)&client_address,&client_addrlen);

//将fd加入到epoll的内核事件表中
addfd(epollfd,connfd,true);
}
else if(events[i].events & EPOLLIN)
{
/*这段代码不会被重复触发,所以我们要循环读取数据,以确保socket读缓存中的所有数据被读出*/

printf("event trigger once\r\n");
while(1)
{
memset(buf,0,BUFFER_SIZE);
int ret = recv(sockfd,buf,BUFFER_SIZE,0);

if(ret < 0 )
{
if((errno == EAGAIN) || (errno == EWOULDBLOCK))
{
printf("read later\r\n");
break;
}
close(sockfd);
break;
}
else if(0 == ret)
{
close(sockfd);
}
else
{
printf("get %d bytes of content: %s\r\n",ret,buf);
}
}
}
}
}

int main(int argc,char* argv[])
{
if(argc <=2)
{
printf("usage:ddddd");
return 1;
}

const char* ip = argv[1];
int port = atoi(argv[2]);

int ret = 0;
struct sockaddr_in address;
bzero(&address,sizeof(address));
address.sin_family = AF_INET;
inet_pton(AF_INET,ip,&address.sin_addr);
address.sin_port = htons(port);

int listenfd = socket(AF_INET,SOCK_STREAM,0);
assert(listenfd >=0);

ret = bind(listenfd,(struct sockaddr*)&address,sizeof(address));
assert(ret != -1);

ret = listen(listenfd,5);
assert(ret!=-1);

epoll_event events[MAX_EVENT_NUMBER];
int epollfd = epoll_create(5);
assert(epollfd!=-1);

addfd(epollfd,listenfd,true);
while(1)
{
int ret = epoll_wait(epollfd,events,MAX_EVENT_NUMBER,-1);
//判断返回值
if(ret < 0)
{
printf("epoll failure!");
break;
}

//lt(events,ret,epollfd,listenfd);
et(events,ret,epollfd,listenfd);
}
close(listenfd);
return 0;
}