程序如下;
#include  
#include  
#include  
#include  
#include  
#include  
#include  
#include  
#include  
#include  
#include   
#include   

#define  PORT 8801    /*监听端口号*/

main(void)
{ 
int sockfd,new_fd;                      /*socket描述符*/
struct sockaddr_in server_addr;         /*socket结构*/
struct sockaddr_in client_addr;         /*socket结构*/
int sin_size,portnumber=PORT;
pthread_t id;
int i,ret;
char hello[]="Hello! World!n";

/* 服务器端开始建立socket描述符 */ 
if((sockfd=socket(AF_INET,SOCK_STREAM,0))==-1) 
{ 
        fprintf(stderr,"Socket error:%sna",strerror(errno));
        exit(1);
}
/* 服务器端填充 sockaddr结构  */ 
bzero(&server_addr,sizeof(struct sockaddr_in)); 
server_addr.sin_family=AF_INET; 
server_addr.sin_addr.s_addr=htonl(INADDR_ANY); 
server_addr.sin_port=htons(portnumber);

/* 捆绑sockfd描述符  */  
if(bind(sockfd,(struct sockaddr *)(&server_addr),sizeof(struct sockaddr))==-1) 
{
        fprintf(stderr,"Bind error:%sna",strerror(errno)); 
        exit(1);
} 
/* 监听sockfd描述符  */ 
if(listen(sockfd,5)==-1)
{
        fprintf(stderr,"Listen error:%sna",strerror(errno)); 
        exit(1);
} 

        /* 服务器阻塞,直到客户程序建立连接  */ 
        sin_size=sizeof(struct sockaddr_in);
        if((new_fd=accept(sockfd,(struct sockaddr *)(&client_addr),&sin_size))==-1)
        { 
                fprintf(stderr,"Accept error:%sna",strerror(errno)); 
                exit(1); 
        }

        fprintf(stderr,"Server get connection from %sn",inet_ntoa(client_addr.sin_addr));
        
        int err;
        fd_set fdR; 
        struct timeval timeout ;
        timeout.tv_sec=10;
        timeout.tv_usec=0;
     
        while(1) {   
                FD_ZERO(&fdR);
                FD_SET(new_fd, &fdR);           
        
                err=select(new_fd + 1, &fdR, NULL, NULL, &timeout);
                
                if(err==-1){
                          printf("error!n");
                          break;                /*error handled by u; */
                       
                }
                else if(err==0){
                          printf("timeout!n");/*timeout hanled by u;*/ 
                       
                }
               else
                   if (FD_ISSET(*fd,&fdR)) { 
                                   printf("read or rev!n");
                   }  
           }
                
close(new_fd);   
        close(sockfd);
   exit(0);
}

你的程序有2个地方有问题
timeout.tv_sec=10;
timeout.tv_usec=0;
要放在 while（） 循环内部，select执行完毕会清空 timeout

if (FD_ISSET(*fd,&fdR)) { 
                                   printf("read or rev!n");
                   }  
你必须read以下*fd,将数据取走，否则内核不会请空标志位