多路I/O转接服务器

多路IO转接服务器也叫做多任务IO服务器。该类型服务器实现的主旨思想是，不在由应用程序自己监视连接，取而代之由内核替应用程序监视文件
主要使用方法有三种

1、select 能监听的文件描述符个数受限于FD_SETSIZE,一般为1024，单纯改变进程打开的文件描述符个数能改变select监听文件个数
2、解决1024以下客户端时使用select是很合适的，但如果连接客户端过多，select采用的是轮询模型，会大大降低服务器响应效率

#include
#include 
#include 
#include 
int select(int nfds,fd_set *readfds,fd_set *writefds,
				fd_set *exceptfds,struct timeval *timeout);

nfds:监控的文件描述符集里最大文件描述符加1，因为此参数会告诉内核检测前多少个文件描述符的状态
readfds:监控有读数据到到文件描述符集合，传入传出参数
writefds:监控写数据到达文件描述符集合，传入传出参数
exceptfds:监控异常发生文件描述符集合，如带外数据到达异常，传入传出参数
timeout:定时阻塞监控时间，3种情况
1、NULL，永远等下去
2、设置timeval,等待固定时间
3、设置timeval里时间均为0，检查描述字后立即返回，轮询

struct timeval{
	long tv_sec; 
	long tv_usec;
};
void FD_CLR(int fd,fd_set *set);//把文件描述符集合里fd清0
int FD_ISSET(int fd,fd_set *set);//测试文件描述符集合里fd是否置1
void FD_SET(int fd,fd_set*set);//把文件描述符集合里fd置1
void FD_ZERO(fd_set *set);//把文件描述符集合里所有位清0

server.c

#include 
#include 
#include 
#include 
#include 

#define MAXLINE 80
#define SERV_PORT 6666

int main(argc,argv[])
{
	int i,maxi,maxfd,listenfd,connfd,sockfd;
	int nready,client[FD_SETSIZE];
	ssize_t n;
	fd_set rset,allset;
	char buf[MAXLINE];
	char str[INET_ADDRSTRLEN]; 
	socklen_t cliaddr_len;
	struct sockaddr_in cliaddr,servaddr;
	listenfd = socket(AF_INET,SOCK_STREAM,0);
	bzero(&servaddr,sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
	servaddr.sin_port = htons(SERV_PORT);
	bind(listenfd,(struct sockaddr*)&servaddr,sizeof(servaddr));
	listen(listenfd,20); 
	maxfd = listenfd; //初始化
	maxi = -1; //client[]的下标
	
	for(i=0;imaxfd)
			{maxfd = connfd;}
			if(i>maxi)
				maxi = i; 
			if(--nready == 0)
			{continue;}					
		}
		for(i=0;i<=maxi;i++){
			if((sockfd = client[i])<0)
				{continue;}
			if(FD_ISSET(sockfd,&rset)){
				if((n==read(sockfd,buf,MAXLINE))==0){
					close(sockfd); 
					FD_CLR(sockfd,&allset);
					client[i] = -1;
				}else{
					int j;
					for(j=0;j 
client.c
 
#include 
#include 
#include 
#include 
#include "wrap.h"

#define MAXLINE 80
#define SERV_PORT 6666

int main(int argc, char *argv[])
{
	struct sockaddr_in servaddr;
	char buf[MAXLINE];
	int sockfd, n;
sockfd = socket(AF_INET, SOCK_STREAM, 0);

	bzero(&servaddr, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	inet_pton(AF_INET, "127.0.0.1", &servaddr.sin_addr);
	servaddr.sin_port = htons(SERV_PORT);

	connect(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr));

	while (fgets(buf, MAXLINE, stdin) != NULL) {
		write(sockfd, buf, strlen(buf));
		n = read(sockfd, buf, MAXLINE);
		if (n == 0)
			printf("the other side has been closed.n");
		else
			write(STDOUT_FILENO, buf, n);
	}
	close(sockfd);
	return 0;
}
 
2 poll函数 
#include 
int poll(struct pollfd *fds,nfds_t nfds,int timeout);

struct pollfd{
	int fd;
	short events;
	short revents; 
}
 
server.c
 
#include 
#include 
#include 
#include 
#include 
#incldue 
#include 

#define MAXLINE 80
#define SERV_PORT 5000
#define OPEN_MAX 1024

int main (int argc,char *argv[])
{
	int i,j,maxi,listenfd,connfd,sockfd;
	int nready;
	ssize_t n;
	char buff[MAXLINE],str[INET_ADDRSTRLEN];
	socklen_t clilen;
	struct pollfd client[OPEN_MAX];
	struct sockaddr_in cliaddr,servaddr;
	
	listenfd = socket(AF_INET,SOCK_STREAM,0);

	bzero(&servaddr,sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
	servaddr.sin_port = htons(SERV_PORT);
	
	bind(listenfd,(struct sockaddr*)&servaddr,sizeof(servaddr));

	listen(listenfd,20);
	
	client[0].fd = listenfd;
	client[0].events = POLLRDNORM; 
	
	for(i = 1;i maxi)
			{maxi = i;}
			
			if(--nready <= 0)
			{continus;}
		}
		for(i = 1;i 
cleint.c
 
#include 
#include 
#include 
#include 

#define MAXLINE 80
#define SERV_PORT 5000

int main (int argc,char *argv[])
{
	struct sockaddr_in servaddr;
	char buf[MAXLINE];
	int sockfd,n;

	sockfd = socket(AF_INET,SOCK_STREAM,0);
	bzero(&servaddr,sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	int_pton(AF_INET,"127.0.0.1",&servaddr.sin_addr);
	servaddr.sin_port = htons(SERV_PORT);
	
	connect(sockfd,(struct sockaddr*)&servaddr,sizeof(servaddr));

	while(fgets(buf,MAXLINE,stdin)!= NULL){
		write(sockfd,buf,strlen(buf));
		n = read(sockfd,buf,MAXLINE);
		if(n == 0)
		{printf("the other side has benn closed.n");}
		else
		{write(STDOUT_FILENO,buf,n);}
	}
	close(sockfd);
	return 0;
}