1. epoll原理
原理性的知識不再另做說明,我在這裏附上收藏整理的兩篇經典文章:
2. epoll服務器端經典示例
2.1 邏輯框架
2.2 代碼
#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 true 1
#define false 0
#define MAX_EVENT_NUMBER 1024
#define BUFFER_SIZE 10
/*將文件描述符設置爲非阻塞*/
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;
}
/*將文件描述符fd上的EPOLLIN註冊到epollfd指示的epoll內核事件表中。 參數enable_et 指定是否對fd採用ET模式*/
void addfd(int epollfd, int fd, int enable_et)
{
struct 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);
}
/*LT 模式的工作原理*/
void lt(struct epoll_event *events, int number, int epollfd, int listenfd)
{
char buf[BUFFER_SIZE];
int i = 0;
for(i= 0;i<number;i++){
int sockfd = events[i].data.fd;
if(sockfd == listenfd){
struct sockaddr_in client_address;
socklen_t client_addrlength = sizeof(client_address);
int connfd = accept(listenfd, (struct sockaddr *)&client_address, &client_addrlength);
addfd(epollfd, connfd, false);
}else if(events[i].events & EPOLLIN){
/*只要socket讀緩存中的還有未讀的數據,此代碼就能觸發*/
printf("event trigger once\n");
memset(buf, 0, BUFFER_SIZE);
int ret = recv(sockfd, buf, BUFFER_SIZE-1, 0);
if(ret <= 0){
close(sockfd);
continue;
}
printf("get %d bytes of content: %s\n", ret, buf);
}else{
printf("Something else happen !!!\n");
}
}
}
/*ET 模式的工作流程*/
void et(struct epoll_event* events, int number, int epollfd, int listenfd)
{
char buf[BUFFER_SIZE];
int i=0;
for(i =0; i<number; i++){
int sockfd = events[i].data.fd;
if(sockfd == listenfd){
struct sockaddr_in client_address;
socklen_t client_addrlength = sizeof(client_address);
int connfd = accept(listenfd, (struct sockaddr* )&client_address, &client_addrlength);
addfd(epollfd, connfd, true);/*對connfd開啓ET模式*/
}else if(events[i].events & EPOLLIN){
/*這段代碼不會被重複觸發,所以我們循環讀取數據,以確保把socket緩衝區的數據全部讀取*/
printf("Event trigger once !!!\n");
while(1){
memset(buf, 0, BUFFER_SIZE);
int ret = recv(sockfd, buf, BUFFER_SIZE-1, 0);
if(ret < 0){
/*對於非阻塞IO,下面的事件成立標識數據已經全部讀取完畢。此後,epoll就能再次觸發sockfd上的sockfd的EPOLLIN事件,以驅動下一次讀操作*/
if((errno == EAGAIN) || (errno == EWOULDBLOCK)){
printf("read later\n");
break;
}
close(sockfd);
break;
}else if(ret == 0){
close(sockfd);
}else{
printf("get %d bytes of content: %s\n", ret, buf);
}
}
}else{
printf("something else happen\n");
}
}
}
int main(int argc, char *argv[])
{
if(argc <= 2){
printf("Usage: %s ip_address port_number\n", 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(AF_INET, SOCK_STREAM, 0);
assert(listenfd >= 0);
ret = bind(listenfd, (struct sockaddr *)&address, sizeof(address));
assert(ret != -1);
int opt = 1;
setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
ret = listen(listenfd, 5);
assert(ret != -1);
struct 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);
if(ret<0){
printf("epoll failure\n");
break;
}
//lt(events, ret, epollfd, listenfd);
et(events, ret, epollfd, listenfd);
}
close(listenfd);
return 0;
}