服务器端编程实例(二 单进程并发_IO多路复用)
2.1)select
函数语法：
/* According to POSIX 1003.1-2001 */
#include <sys/select.h>
/* According to earlier standards */
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>
int select(int n, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeout);
int pselect(int n, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, const struct timespec *timeout, const sigset_t
*sigmask);
FD_CLR(int fd, fd_set *set);
FD_ISSET(int fd, fd_set *set);
FD_SET(int fd, fd_set *set);
FD_ZERO(fd_set *set);
DESCRIPTION
The functions select and pselect wait for a number of file descriptors to change status.
RETURN VALUE
On success, select and pselect return the number of descriptors contained in the descriptor sets, which may be zero if the timeout expires before anything interesting happens. On error, -1 is returned, and errno is set appropriately; the sets and timeout become undefined, so do not rely on their contents after an error.
示例：
#include <stdio.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>
int main (void)
{
fd_set rfds;
struct timeval tv;
int retval;
/* Watch stdin (fd 0) to see when it has input. */
FD_ZERO (&rfds);
FD_SET (0, &rfds);
FD_SET (1, &rfds);
FD_SET (2, &rfds);
FD_SET (4, &rfds);
/* Wait up to five seconds. */
tv.tv_sec = 5;
tv.tv_usec = 0;
retval = select (2, &rfds, NULL, NULL, &tv);
if (retval == -1)
perror ("select()");
else if (retval)
{
printf ("Data is available now./n");
printf( "retval=%d/n",retval);
}
/* FD_ISSET(0, &rfds) will be true. */
else
printf ("No data within five seconds./n");
return 0;
}
2.2)epoll
SYNOPSIS
#include <sys/epoll.h>
int epoll_ctl(int epfd, int op, int fd, struct epoll_event *event)
int epoll_create(int size)
int epoll_wait(int epfd, struct epoll_event * events, int maxevents, int timeout)
示例：
#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>
#define MAXLINE 10
#define OPEN_MAX 100
#define LISTENQ 20
#define SERV_PORT 5555
#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 = 0;
char line[MAXLINE];
int l_sinSize = 0;
l_sinSize = sizeof(struct sockaddr);
//声明epoll_event结构体的变量,ev用于注册事件,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设置为非阻塞方式
setnonblocking(listenfd);//-----------------------------
//设置与要处理的事件相关的文件描述符
ev.data.fd = listenfd;//--------------------------------
//设置要处理的事件类型
ev.events = EPOLLIN|EPOLLET;//--------------------------
//注册epoll事件
epoll_ctl(epfd, EPOLL_CTL_ADD, listenfd, &ev);//---------------------
bzero(&serveraddr, sizeof(struct sockaddr_in));
serveraddr.sin_family = AF_INET;
serveraddr.sin_addr.s_addr = htonl(INADDR_ANY);
serveraddr.sin_port = htons(SERV_PORT);
bind(listenfd, (struct sockaddr *)(&serveraddr), sizeof(struct sockaddr));
listen(listenfd, LISTENQ);
maxi = 0;
for ( ; ; ) {
//等待epoll事件的发生
nfds=epoll_wait(epfd,events,20,500);//---------------------------
//处理所发生的所有事件
for (i = 0; i < nfds; ++i)
{
if (events[i].data.fd == listenfd)
{
connfd = accept(listenfd, (struct sockaddr *)(&clientaddr), (socklen_t *)&l_sinSize);//------------
if (connfd < 0)
{
perror("connfd < 0");
exit(1);
}
setnonblocking(connfd);
char* str = inet_ntoa(clientaddr.sin_addr);
std::cout<<"connect from "<<str<<std::endl;
//设置用于读操作的文件描述符
ev.data.fd = connfd;
//设置用于注测的读操作事件
ev.events = EPOLLIN|EPOLLET;
//注册ev
epoll_ctl(epfd, EPOLL_CTL_ADD, connfd, &ev);
}
else if (events[i].events&EPOLLIN)
{
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;
}
//设置用于写操作的文件描述符
ev.data.fd = sockfd;
//设置用于注测的写操作事件
ev.events = EPOLLOUT|EPOLLET;
//修改sockfd上要处理的事件为EPOLLOUT
epoll_ctl(epfd, EPOLL_CTL_MOD, sockfd, &ev);
}
else if(events[i].events&EPOLLOUT)
{
sockfd = events[i].data.fd;
ssize_t l_writeSize = write(sockfd, line, n);
std::cout<<"write "<<l_writeSize<<std::endl;
//设置用于读操作的文件描述符
ev.data.fd = sockfd;
//设置用于注测的读操作事件
ev.events = EPOLLIN|EPOLLET;
//修改sockfd上要处理的事件为EPOLIN
epoll_ctl(epfd, EPOLL_CTL_MOD, sockfd, &ev);
}
}
}
}