IO复用，说得粗鄙一点，就是不用开多线程也能发送和接收消息。不多说，看代码：(select和poll是别人写的。引用一下，别见怪。)
select：
#include <stdio.h>
#include <string.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/select.h>
const static int MAXLINE = 1024;
const static int SERV_PORT = 10001;
int main()
{
int i , maxi , maxfd, listenfd , connfd , sockfd ;
/*nready 描述字的数量*/
int nready ,client[FD_SETSIZE];
int n ;
/*创建描述字集合，由于select函数会把未有事件发生的描述字清零，所以我们设置两个集合*/
fd_set rset , allset;
char buf[MAXLINE];
socklen_t clilen;
struct sockaddr_in cliaddr , servaddr;
/*创建socket*/
listenfd = socket(AF_INET , SOCK_STREAM , 0);
/*定义sockaddr_in*/
memset(&servaddr , 0 ,sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(SERV_PORT);
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
bind(listenfd, (struct sockaddr *) & servaddr , sizeof(servaddr));
listen(listenfd , 100);
/*listenfd 是第一个描述字*/
/*最大的描述字，用于select函数的第一个参数*/
maxfd = listenfd;
/*client的数量，用于轮询*/
maxi = -1;
/*init*/
for(i=0 ;i<FD_SETSIZE ; i++)
client[i] = -1;
FD_ZERO(&allset);
FD_SET(listenfd, &allset);
for (;;)
{
rset = allset;
/*只select出用于读的描述字，阻塞无timeout*/
nready = select(maxfd+1 , &rset , NULL , NULL , NULL);
if(FD_ISSET(listenfd,&rset))
{
clilen = sizeof(cliaddr);
connfd = accept(listenfd , (struct sockaddr *) & cliaddr , &clilen);
/*寻找第一个能放置新的描述字的位置*/
for (i=0;i<FD_SETSIZE;i++)
{
if(client[i]<0)
{
client[i] = connfd;
break;
}
}
/*找不到，说明client已经满了*/
if(i==FD_SETSIZE)
{
printf("Too many clients , over stack .\n");
return -1;
}
FD_SET(connfd,&allset);//设置fd
/*更新相关参数*/
if(connfd > maxfd) maxfd = connfd;
if(i>maxi) maxi = i;
if(nready<=1) continue;
else nready --;
}
for(i=0 ; i<=maxi ; i++)
{
if (client[i]<0) continue;
sockfd = client[i];
if(FD_ISSET(sockfd,&rset))
{
n = read(sockfd , buf , MAXLINE);
if (n==0)
{
/*当对方关闭的时候，server关闭描述字，并将set的sockfd清空*/
close(sockfd);
FD_CLR(sockfd,&allset);
client[i] = -1;
}
else
{
buf[n]=‘\0‘;
printf("Socket %d said : %s\n",sockfd,buf);
write(sockfd,buf,n); //Write back to client
}
nready --;
if(nready<=0) break;
}
}
}
return 0;
}
poll：
#include <stdio.h>
#include <string.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <poll.h>
/*环境为ubuntu10.04自带c环境，无法自动引入下列宏，所以自己写在前面了*/
#define INFTIM -1
#define POLLRDNORM 0x040 /* Normal data may be read. */
#define POLLRDBAND 0x080 /* Priority data may be read. */
#define POLLWRNORM 0x100 /* Writing now will not block. */
#define POLLWRBAND 0x200 /* Priority data may be written. */
#define MAXLINE 1024
#define OPEN_MAX 16 //一些系统会定义这些宏
#define SERV_PORT 10001
int main()
{
int i , maxi ,listenfd , connfd , sockfd ;
int nready;
int n;
char buf[MAXLINE];
socklen_t clilen;
struct pollfd client[OPEN_MAX];
struct sockaddr_in cliaddr , servaddr;
listenfd = socket(AF_INET , SOCK_STREAM , 0);
memset(&servaddr,0,sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(SERV_PORT);
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
bind(listenfd , (struct sockaddr *) & servaddr, sizeof(servaddr));
listen(listenfd,10);
client[0].fd = listenfd;
client[0].events = POLLRDNORM;
for(i=1;i<OPEN_MAX;i++)
{
client[i].fd = -1;
}
maxi = 0;
for(;;)
{
nready = poll(client,maxi+1,INFTIM);
if (client[0].revents & POLLRDNORM)
{
clilen = sizeof(cliaddr);
connfd = accept(listenfd , (struct sockaddr *)&cliaddr, &clilen);
for(i=1;i<OPEN_MAX;i++)
{
if(client[i].fd<0)
{
client[i].fd = connfd;
client[i].events = POLLRDNORM;
break;
}
}
if(i==OPEN_MAX)
{
printf("too many clients! \n");
}
if(i>maxi) maxi = i;
nready--;
if(nready<=0) continue;
}
for(i=1;i<=maxi;i++)
{
if(client[i].fd<0) continue;
sockfd = client[i].fd;
if(client[i].revents & (POLLRDNORM|POLLERR))
{
n = read(client[i].fd,buf,MAXLINE);
if(n<=0)
{
close(client[i].fd);
client[i].fd = -1;
}
else
{
buf[n]=‘\0‘;
printf("Socket %d said : %s\n",sockfd,buf);
write(sockfd,buf,n); //Write back to client
}
nready--;
if(nready<=0) break; //no more readable descriptors
}
}
}
return 0;
}
epoll：
#include <stdio.h>
#include <string.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <poll.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <fcntl.h>
#include <sys/epoll.h>
#include <sys/time.h>
#include <sys/resource.h>
#define MAXLINE 1024
#define OPEN_MAX 16 //一些系统会定义这些宏
#define SERV_PORT 10001
int main()
{
int i , maxi ,listenfd , connfd , sockfd ,epfd, nfds;
int n;
char buf[MAXLINE];
struct epoll_event ev, events[20];
socklen_t clilen;
struct pollfd client[OPEN_MAX];
struct sockaddr_in cliaddr , servaddr;
listenfd = socket(AF_INET , SOCK_STREAM , 0);
memset(&servaddr,0,sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(SERV_PORT);
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
bind(listenfd , (struct sockaddr *) & servaddr, sizeof(servaddr));
listen(listenfd,10);
epfd = epoll_create(256);
ev.data.fd=listenfd;
ev.events=EPOLLIN|EPOLLET;
epoll_ctl(epfd,EPOLL_CTL_ADD,listenfd,&ev);
for(;;)
{
nfds=epoll_wait(epfd,events,20,500);
for(i=0; i<nfds; i++)
{
if (listenfd == events[i].data.fd)
{
clilen = sizeof(cliaddr);
connfd = accept(listenfd , (struct sockaddr *)&cliaddr, &clilen);
if(connfd < 0)
{
perror("connfd < 0");
exit(1);
}
ev.data.fd=connfd;
ev.events=EPOLLIN|EPOLLET;
epoll_ctl(epfd,EPOLL_CTL_ADD,connfd,&ev);
}
else if (events[i].events & EPOLLIN)
{
if ( (sockfd = events[i].data.fd) < 0)
continue;
n = recv(sockfd,buf,MAXLINE,0);
if (n <= 0)
{
close(sockfd);
events[i].data.fd = -1;
}
else
{
buf[n]=‘\0‘;
printf("Socket %d said : %s\n",sockfd,buf);
ev.data.fd=sockfd;
ev.events=EPOLLOUT|EPOLLET;
epoll_ctl(epfd,EPOLL_CTL_MOD,connfd,&ev);
}
}
else if( events[i].events&EPOLLOUT )
{
sockfd = events[i].data.fd;
send(sockfd, "Hello!", 7, 0);
ev.data.fd=sockfd;
ev.events=EPOLLIN|EPOLLET;
epoll_ctl(epfd,EPOLL_CTL_MOD,sockfd,&ev);
}
else
{
printf("This is not avaible!");
}
}
}
close(epfd);
return 0;
}
时间： 2025-01-14 16:19:59