select_socket 网络超时编程实例

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <strings.h>
#include <string.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/types.h>          /* See NOTES */
#include <sys/socket.h>
#include <sys/un.h>
#include <linux/in.h>
#define N 100
/*
   int select(int nfds, fd_set *readfds, fd_set *writefds,
   fd_set *exceptfds, struct timeval *timeout);

   void FD_CLR(int fd, fd_set *set);
   int  FD_ISSET(int fd, fd_set *set);
   void FD_SET(int fd, fd_set *set);
   void FD_ZERO(fd_set *set);
   */
int main(void)
{
 int sokfd;
 int connfd;
 struct sockaddr_in  sev_sockaddr;
 struct sockaddr_in  client_sockaddr;

 fd_set readfds;
 fd_set readfdstemp;
 int nfds;

 int i=0;
 int recvn=0;
 char buf[N];
   

 int client_sockaddr_len=sizeof(client_sockaddr);
 if(( sokfd=socket(AF_INET,SOCK_STREAM,0))==-1)
 {
  perror("scoket");
  exit(-1);
 }
 bzero(&sev_sockaddr,sizeof(sev_sockaddr));
 sev_sockaddr.sin_family=AF_INET;
 sev_sockaddr.sin_port=htons(9000);
 sev_sockaddr.sin_addr.s_addr=inet_addr("192.168.1.100");
 if(bind(sokfd,(struct sockaddr*)&sev_sockaddr,sizeof(sev_sockaddr))==-1)
 {
  perror("bind");
  exit(-1);
 }
 listen(sokfd,5);
 struct  timeval timeo={5,0};
 FD_ZERO(&readfds);
 FD_SET(sokfd,&readfds);
 nfds=sokfd;

 while(1)
 {

     //FD_ZERO(&readfds);
      //FD_SET(sokfd,&readfds);
  readfdstemp=readfds;
  //timeo={5,0};
  timeo.tv_sec=5;
  timeo.tv_usec=0;
  /*************************************************************************
    timeout is an upper bound on the amount of time elapsed before select()
    returns.   If  both  fields  of  the  timeval  stucture  are zero, then
    select() returns immediately.  (This is useful for polling.)  If  time鈥?    out is NULL (no timeout), select() can block indefinitely.
   ************************************************************************/
  /*************************************************************************
    On  success,  select() and pselect() return the number of file descrip鈥?    tors contained in the three returned  descriptor  sets  (that  is,  the
    total  number  of  bits  that  are set in readfds, writefds, exceptfds)
    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.
   *********************************************************************/

  int ret=100000;         
  if((ret=select(nfds+1,&readfdstemp,NULL,NULL,&(timeo)))==-1)
  {
   perror("select");
   exit(-1);
  }
  printf("time :%d\n",ret);
  if(ret>0)
  {  
   for(i=0;i<nfds+1;i++)
   {
    if(FD_ISSET(i,&readfdstemp))
    {
     if(i==sokfd)
     {
      connfd=accept(sokfd,(struct sockaddr*)&client_sockaddr,&client_sockaddr_len);
                        nfds=(nfds>connfd)?nfds:connfd;
      FD_SET(connfd,&readfds);
     }
     else
     {
                       bzero(buf,sizeof(buf));
        recvn=recv(i,buf,10,0);
        if(recvn==0)
        {
         close(i);
         FD_CLR(i,&readfds);
         break;
        }
      printf("%s\n",buf);

     }

    }
   }
  }
  else
  {
   printf("the net is timeout...\n");
  }

 }
}