多路选择i/o

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <ctype.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <errno.h>
#include "iolib.h"
#define MAX_LINE 80
int port = 8000;

void my_fun(char *p)
{
       if(p == NULL)
              exit(1);
       for(; *p != ‘‘; p++)
              if(*p >= ‘A‘ && *p <= ‘Z‘)
                     *p = *p - ‘A‘ + ‘a‘;
}
 
int main(void)
{
       struct sockaddr_in sin;
       struct sockaddr_in cin;
       int lfd;
       int cfd;
       int sfd;
       int rdy;
       int client[FD_SETSIZE];          ///客户端连接的套接字描述符数组
       int maxi;
       int maxfd;                                  ///最大连接数
       fd_set rest;
       fd_set allset;
       socklen_t addr_len;                     ///地址结构的长度
       char buf[MAX_LINE];
       char addr_p[INET_ADDRSTRLEN];
       int i, n;
       int len;
       int opt = 1;                         ///套接字选项
       bzero(&sin, sizeof(sin)); ///填充地址结构
       sin.sin_family = AF_INET;
       sin.sin_addr.s_addr = INADDR_ANY;
       sin.sin_port = hton(port);
        /*创建一个面向连接的套接字*/
       lfd = socket(AF_INET, SOCK_STREAM, 0);
       if(lfd == -1)
       {
              perror("call to sock");
              exit(1);
       }
 
       /*设置套接字选项，使用默认选项*/
       setsockopt(lfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
 
       /*绑定套接字到地址结构*/
       n = bind(lfd, (struct sockaddr_in *) &sin, sizeof(opt));
       if(n == -1)
       {
              perror("call to bind");
              exit(1);
       }
 
       /*开始监听连续请求*/
       n = listern(lfd, 20);
       if(n == -1)
       {
              perror("call to listern");
              exit(1);
       }
       printf("Accepting connecting ...
");
       maxfd = lfd;          ///对最大文件描述符进行初始化
       maxi = -1;
       for(i = 0; i < FD_SETSIZE; i++)     ///初始化客户端连接描述符集合
              client[i] = -1;
       FD_ZERO(&allset);               ///清空文件描述符集合
       FD_SET(lfd, &allset);             ///将监听接字设置在集合内
      
       /*开始服务器程序的死循环*/
       while(1)
       {
              rset = allset;
              /*得到当前可以读的文件描述符*/
              rdy = select(maxfd + 1, &rset, NULL, NULL, NULL);
              if(FD_ISSET(lfd, &rest))
              {
                     addr_len = sizeof(cin);
                     /*创建一个链接描述符*/
                     cfd = accept(lfd, (struct sockaddr_in *) &cin, &addr_len);
                     if(cfd == -1)
                     {
                            perror("fail to accept");
                            exit(1);
                     }
                     /*查找一个空闲的位置*/
                     for(i = 0; i < FD_SETSIZE; i++)
                     {
                            if(client[i] < 0)
                            {
                                   client[i] = cfd;
                                   break;
                            }
                     }
                     /*太多的客户端连接，服务器拒绝连接，跳出循环*/
                     if(i == FD_SETSIZE)
                     {
                            printf("too many clients
");
                            exit(1);
                     }
                     FD_SET(cfd, &allset);            ///设置连接集合
                     if(cfd > max_fd)
                            maxfd = cfd;
                     if(i > maxi)
                            maxi = i;
                     if(--rdy <= 0)
                            continue;
              }
 
              for(i = 0; i < maxi; i++)        ///对每一个连接描述符做处理

              {

                     if((sfd = client[i] < 0))

                            continue;

                     if(FD_ISSET(sfd, &rset))
                     {
                            n = my_read(sfd, buf, MAX_LINE);      ///读取数据
                            if(n == 0)
                            {
                                   printf("the other side has been closed
");
                                   fflush(stdout);        ///刷新到输出终端
                                   close(sfd);
                                   FD_CLR(sfd, &allset);    ///清空连接描述符数组
                                   client[i] = -1;
                            }
                           else
                            {
                                   inet_ntop(AF_INET, &cin.sin_addr, addr_p, sizeof(addr_p));
                                   printf("client IP is %s, port is %d
", addr_p, ntohs(cin.sin_port));
                                   my_fun(buf);
                                   n = my_write(sfd, buf, len + 1);
                                   if(n == -1)
                                          exit(1);

                            }
                            if(--rdy <= 0)
                                   break;
                     }
              }
       }
       close(lfd);
       return 0;
}