Not able to receive message in UDP

Question

I am trying to create a parent-child program where parent sends its children the FILE* ptr using unix domain sockets. I am successful in creating the child process but they are not able to receive messages from the parent process. Is there some error in "(FILE*)fd_ptr, 8" part of sendto and recvfrom. I first create a socket in parent process and then fork the process. In the child process, I again create a socket and use it to receive data from parent. Please help!

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <string.h>
#include<sys/wait.h>


#define PORT 4444

void die(char* s){
    perror(s);
    exit(EXIT_FAILURE);
}

int main(){
    int sockfd;
    struct sockaddr_in servaddr_p;
    struct sockaddr_in servaddr_c;
    int len = sizeof(servaddr_p);    
    if((sockfd = socket(AF_INET, SOCK_DGRAM, 0))<0)
        die("socket creation failed");
       
    memset(&servaddr_p, 0, sizeof(servaddr_p));    
    servaddr_p.sin_family = AF_INET; // IPv4
    servaddr_p.sin_addr.s_addr = INADDR_ANY;
    servaddr_p.sin_port = htons(PORT);
    
    if(bind(sockfd, (const struct sockaddr*)&servaddr_p, sizeof(servaddr_p))<0)
        die("bind failed");       
    FILE* fd = fopen("/home/johnny/Desktop/q3/0.txt", "r");
        
    for(int i = 0; i<2; ++i){
        int pid=fork();           
        if(pid==0){
            sleep(1);   //receiving data from parent
            int* fd_ptr;
            memset(&servaddr_c, 0, sizeof(servaddr_c));
            servaddr_c.sin_family = AF_INET;
            servaddr_c.sin_port = htons(PORT);
            servaddr_c.sin_addr.s_addr = INADDR_ANY;
            if(recvfrom(sockfd, (FILE*)fd_ptr, 8, 0, (struct sockaddr*)&servaddr_p, &len)<0)
                die("msg not received");
            exit(0);
        }       
        else{
            FILE *fd_ptr = fd;    //sending data to children
            sendto(sockfd, (FILE*)fd_ptr, 8, 0, (struct sockaddr*)&servaddr_c, len);
        }              
    }
    pid_t child_pid, wpid;
    int status = 0;
    while ((wpid = wait(&status)) > 0);
    close(fd);
}