The key point is that whether EPOLL will treat the combination of EPOLLET | EPOLLONESHOT and EPOLLLT | EPOLLONESHOT as special case. As I known, it is not. EPOLL just care them seperately. To EPOLLET and EPOLLLT, the different kindly only is in function ep_send_events, if the EPOLLET is set, then the function will call list_add_tail to add the epitem into the ready list in epoll_fd/eventepoll object.
To the EPOLLONESHOT, the role is to disable the fd. So I think the different between them is the different between ET and LT. You can check the result using below codes I think
// server.cc
#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>
#define MAX_EVENT_NUMBER 1024
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 oneshot)
{
epoll_event event;
event.data.fd = fd;
event.events = EPOLLIN | EPOLLET;
if(oneshot)
event.events |= EPOLLONESHOT;
epoll_ctl(epollfd, EPOLL_CTL_ADD, fd, &event);
setnonblocking(fd);
}
// reset the fd with EPOLLONESHOT
void reset_oneshot(int epollfd, int fd)
{
epoll_event event;
event.data.fd = fd;
event.events = EPOLLIN | EPOLLET | EPOLLONESHOT;
epoll_ctl(epollfd, EPOLL_CTL_MOD, fd, &event);
}
int main(int argc, char** argv)
{
if(argc <= 2)
{
printf("usage: %s ip_address port_number\n", basename(argv[0]));
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(PF_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);
addfd(epollfd, listenfd, false);
while(1)
{
printf("next loop: -----------------------------");
int ret = epoll_wait(epollfd, events, MAX_EVENT_NUMBER, -1);
if(ret < 0)
{
printf("epoll failure\n");
break;
}
for(int i = 0; i < ret; i++)
{
int sockfd = events[i].data.fd;
if(sockfd == listenfd)
{
printf("into listenfd part\n");
struct sockaddr_in client_address;
socklen_t client_addrlength = sizeof(client_address);
int connfd = accept(listenfd, (struct sockaddr*)&client_address,
&client_addrlength);
printf("receive connfd: %d\n", connfd);
addfd(epollfd, connfd, true);
// reset_oneshot(epollfd, listenfd);
}
else if(events[i].events & EPOLLIN)
{
printf("into linkedfd part\n");
printf("start new thread to receive data on fd: %d\n", sockfd);
char buf[2];
memset(buf, '\0', 2);
// just read one byte, and reset the fd with EPOLLONESHOT, check whether still EPOLLIN event
int ret = recv(sockfd, buf, 2 - 1, 0);
if(ret == 0)
{
close(sockfd);
printf("foreigner closed the connection\n");
break;
}
else if(ret < 0)
{
if(errno == EAGAIN)
{
printf("wait to the client send the new data, check the oneshot memchnism\n");
sleep(10);
reset_oneshot(epollfd, sockfd);
printf("read later\n");
break;
}
}
else {
printf("receive the content: %s\n", buf);
reset_oneshot(epollfd, sockfd);
printf("reset the oneshot successfully\n");
}
}
else
printf("something unknown happend\n");
}
sleep(1);
}
close(listenfd);
return 0;
}
the Client is
from socket import *
import sys
import time
long_string = b"this is a long content which need two time to fetch"
def sendOneTimeThenSleepAndClose(ip, port):
s = socket(AF_INET, SOCK_STREAM);
a = s.connect((ip, int(port)));
print("connect success: {}".format(a));
data = s.send(b"this is test");
print("send successfuly");
time.sleep(50);
s.close();
sendOneTimeThenSleepAndClose('127.0.0.1', 9999)
