以代码来说明问题:
首先给出server的代码,须要说明的是每次accept的连接,增加可读集的时候採用的都是ET模式,并且接收缓冲区是5字节的,也就是每次仅仅接收5字节的数据:
- #include <iostream>
- #include <sys/socket.h>
- #include <sys/epoll.h>
- #include <netinet/in.h>
- #include <arpa/inet.h>
- #include <fcntl.h>
- #include <unistd.h>
- #include <stdio.h>
- #include <errno.h>
- using namespace std;
- #define MAXLINE 5
- #define OPEN_MAX 100
- #define LISTENQ 20
- #define SERV_PORT 5000
- #define INFTIM 1000
- void setnonblocking(int sock)
- {
- int opts;
- opts=fcntl(sock,F_GETFL);
- if(opts<0)
- {
- perror("fcntl(sock,GETFL)");
- exit(1);
- }
- opts = opts|O_NONBLOCK;
- if(fcntl(sock,F_SETFL,opts)<0)
- {
- perror("fcntl(sock,SETFL,opts)");
- exit(1);
- }
- }
- int main()
- {
- int i, maxi, listenfd, connfd, sockfd,epfd,nfds;
- ssize_t n;
- char line[MAXLINE];
- socklen_t clilen;
- //声明epoll_event结构体的变量,ev用于注冊事件,数组用于回传要处理的事件
- struct epoll_event ev,events[20];
- //生成用于处理accept的epoll专用的文件描写叙述符
- epfd=epoll_create(256);
- struct sockaddr_in clientaddr;
- struct sockaddr_in serveraddr;
- listenfd = socket(AF_INET, SOCK_STREAM, 0);
- //把socket设置为非堵塞方式
- //setnonblocking(listenfd);
- //设置与要处理的事件相关的文件描写叙述符
- ev.data.fd=listenfd;
- //设置要处理的事件类型
- ev.events=EPOLLIN|EPOLLET;
- //ev.events=EPOLLIN;
- //注冊epoll事件
- epoll_ctl(epfd,EPOLL_CTL_ADD,listenfd,&ev);
- bzero(&serveraddr, sizeof(serveraddr));
- serveraddr.sin_family = AF_INET;
- char *local_addr="127.0.0.1";
- inet_aton(local_addr,&(serveraddr.sin_addr));//htons(SERV_PORT);
- serveraddr.sin_port=htons(SERV_PORT);
- bind(listenfd,(sockaddr *)&serveraddr, sizeof(serveraddr));
- listen(listenfd, LISTENQ);
- maxi = 0;
- for ( ; ; ) {
- //等待epoll事件的发生
- nfds=epoll_wait(epfd,events,20,500);
- //处理所发生的全部事件
- for(i=0;i<nfds;++i)
- {
- if(events[i].data.fd==listenfd)
- {
- connfd = accept(listenfd,(sockaddr *)&clientaddr, &clilen);
- if(connfd<0){
- perror("connfd<0");
- exit(1);
- }
- //setnonblocking(connfd);
- char *str = inet_ntoa(clientaddr.sin_addr);
- cout << "accapt a connection from " << str << endl;
- //设置用于读操作的文件描写叙述符
- ev.data.fd=connfd;
- //设置用于注測的读操作事件
- ev.events=EPOLLIN|EPOLLET;
- //ev.events=EPOLLIN;
- //注冊ev
- epoll_ctl(epfd,EPOLL_CTL_ADD,connfd,&ev);
- }
- else if(events[i].events&EPOLLIN)
- {
- cout << "EPOLLIN" << endl;
- if ( (sockfd = events[i].data.fd) < 0)
- continue;
- if ( (n = read(sockfd, line, MAXLINE)) < 0) {
- if (errno == ECONNRESET) {
- close(sockfd);
- events[i].data.fd = -1;
- } else
- std::cout<<"readline error"<<std::endl;
- } else if (n == 0) {
- close(sockfd);
- events[i].data.fd = -1;
- }
- line[n] = '