双管道实现进程数据通信

我用的服务器端程序如下:

#include "cliser.h"
#include<fcntl.h>

int main(int argc,char *argv[])
{
int res,client_fifo_fd;
char *temp_data_ptr;
int read_res;

mkfifo(SERVER_FIFO_NAME,0777);
res = open(SERVER_FIFO_NAME,O_RDONLY);
if(res == -1)
{
printf("open read server_fifo_name failure/n");
exit(EXIT_FAILURE);
}

printf("res == %d/n",res);
read_res = read(res,temp_data_ptr,256);
printf("read_res = %d/n",read_res);
if(read_res > 0)
{
printf(">>>>>>>>>>>>>>>>>>>>>>>>>>>>server.c/n");
printf("get data from client /n");
printf("data was %s/n",temp_data_ptr);
while(*temp_data_ptr)
{
*temp_data_ptr = toupper(*temp_data_ptr+1);
temp_data_ptr++;
}
client_fifo_fd = open(CLIENT_FIFO_NAME,O_WRONLY);
if(client_fifo_fd == -1)
{
printf("open write client_fifo_name/n");
exit(EXIT_FAILURE);
}
write(client_fifo_fd,temp_data_ptr,BUFFER_SIZE);
}
close(client_fifo_fd);
exit(EXIT_SUCCESS);
}

客户程序如下:#include "cliser.h"
#include<fcntl.h>

int main(int argc,char *argv[])
{
int res;
char buffer[BUFFER_SIZE];
int write_res;
int read_res;
int client_fifo_fd;

memset(buffer,'/0',strlen(buffer));
memcpy(buffer,"Hello world",30);

// unlink(SERVER_FIFO_NAME);
res = open(SERVER_FIFO_NAME,O_WRONLY);
printf("res = %d/n",res);
if(res == -1)
{
printf("open %s write Failure/n",SERVER_FIFO_NAME);
exit(EXIT_FAILURE);
}
write_res = write(res,buffer,strlen(buffer));
if(write_res > 0)
{
printf("*****************************client.c/n");
printf("write some data in fifo/n");
printf("data content was %s/n",buffer);
}

mkfifo(CLIENT_FIFO_NAME,0777);
sleep(5);
client_fifo_fd = open(CLIENT_FIFO_NAME,O_RDONLY);

if(client_fifo_fd == -1)
{
printf("CLinet_fifo_name no write data/n");
exit(EXIT_FAILURE);
}

read_res = read(client_fifo_fd,buffer,strlen(buffer));
if(read_res > 0)
{
printf("from client_fifo fetch data/n");
printf("data content was %s/n",buffer);
}

close(res);
close(client_fifo_fd);
exit(EXIT_SUCCESS);
}
在运行过程中,红色标记的地方通不过,请问可以哪位大哥帮我看下,server从阻塞状态到执行过程中res = 3;但read_res = -1?不知为何解;