named pipe에서 데이터를 읽기 위해 select를 사용하는데 질문이 있습니다.

halfduplex.h
#define HALF_DUPLEX	"/tmp/halfduplex"
#define MAX_BUF_SIZE	255

server.c
 
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <ctype.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include "halfduplex.h" /* For name of the named-pipe */
#include <sys/time.h>
 
int main(int argc, char *argv[])
{
    int fd, ret_val, count, numread;
    char buf[MAX_BUF_SIZE];
 
        int is_select;
        fd_set fd_read;
        struct timeval  time_val;
 
    /* Create the named - pipe */
    ret_val = mkfifo(HALF_DUPLEX, 0666);
 
    if ((ret_val == -1) && (errno != EEXIST)) {
        perror("Error creating the named pipe");
        exit (1);
    }
 
 
    /* Open the pipe for reading */
//    fd = open(HALF_DUPLEX, O_RDONLY);
    fd = open(HALF_DUPLEX, O_NONBLOCK);
 
    /* Read from the pipe */
        while (1)
{
        FD_ZERO(&fd_read);
        FD_SET(fd, &fd_read);
 
        time_val.tv_sec = 1;
        time_val.tv_usec = 0;
        is_select = select(fd+1, &fd_read, NULL, NULL, &time_val);
 
 
        if (is_select > 0)
        {
            numread = read(fd, buf, MAX_BUF_SIZE);
            buf[numread] = 0;
 
            printf("Half Duplex Server : Read From the pipe : %s\n", buf);
                if (buf[0] == 'x')
                        break;
 
        }
        else
                printf("Noting to read...\n");
}
 
        return 0;
}

client.c
#include <stdio.h>
#include <errno.h>
#include <ctype.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include "halfduplex.h" /* For name of the named-pipe */
 
int main(int argc, char *argv[])
{
    int fd;
        char buf[100];
 
 
    /* Check if an argument was specified. */
 
 
    /* Open the pipe for writing */
    fd = open(HALF_DUPLEX, O_WRONLY);
    close(fd);
 
   return 0;
}