Not able to pass strings through named pipes (FIFOs) in multithreaded processes - c

Question

I am trying to use 'FIFOs' and 'popen()' function for communication between multiple processes. Also, the first process is multithreaded for reading and writing operations.
Following is the C code for the processes:
P1 process (Q1.c)
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <pthread.h>
#include <errno.h>
void* reader()
{
char string[64];
int rfd = open("FIFO",O_RDONLY);
while(1)
{
read(rfd,string,sizeof(string));
sleep(10);
printf("%s\n",string);
}
}
void* writer()
{
char string[64];
FILE *wfd = popen("./Q1_1","w");
int fd = fileno(wfd);
while(1)
{
scanf("%s",string);
write(fd,string,sizeof(string));
}
pclose(wfd);
}
int main()
{
if(mkfifo("FIFO",0666)==-1)
{
if(errno!=EEXIST)
{
return 1;
}
}
pthread_t r_thread,s_thread;
pthread_create(&r_thread,NULL,reader,NULL);
pthread_create(&s_thread,NULL,writer,NULL);
pthread_join(r_thread,NULL);
pthread_join(s_thread,NULL);
return 0;
}
P2 Process (Q1_1.c)
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <pthread.h>
#include <errno.h>
int main()
{
FILE *fd = popen("./Q1_2","w");
char string[64];
int ffd = fileno(fd);
printf("P2Check");
while(1)
{
scanf("%s",string);
write(ffd,string,sizeof(string));
}
return 0;
}
P3 Process (Q1_2.c)
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <pthread.h>
#include <errno.h>
int main()
{
char string[64];
if(mkfifo("FIFO",0666)==-1)
{
if(errno!=EEXIST)
{
return 1;
}
}
int wfd = open("FIFO",O_WRONLY);
printf("P3Check");
while(1)
{
scanf("%s",string);
write(wfd,string,sizeof(string));
}
}
However, after executing process P1 and providing input, there is no output as if the process is stuck. I suspect there is some issue with the multithreading but not sure.