Get IP addresses of all devices connected (UDP) - c

Question

I have looked for a similar question, but I could not find one that would work for me. I am doing a simple project for one of my subjects, but I never had experience with sockets, so I need some help with the implementation of one feature.
Basically, there are several units interconnected by a communication network (physical ETHERNET 1Gbps, TCP / IP protocol), and I have to be able to communicate with all the boards. I can implement all other features I need on one specific board, but I don't know how to manipulate all the boards simultaneously.
So, the question is: how to get a list of all boards connected and how to select which board should receive/send a message?
Big thanks to anyone who would help.
#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <time.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <string.h>
#include "mzapo_parlcd.h"
#include "mzapo_phys.h"
#include "mzapo_regs.h"
#define MY_PORT 55555
#define BUFLEN 512
int main(int argc, char *argv[])
{
int sockfd;
char buffer[BUFLEN];
struct sockaddr_in peeraddr;
// SET UP A NETWORK SOCKET
if ((sockfd = socket (AF_INET, SOCK_DGRAM, 0)) == -1) {
perror("socket");
exit(1);
}
int broadcast = 1;
if (setsockopt (sockfd, SOL_SOCKET, SO_BROADCAST, & broadcast,
sizeof broadcast) == -1) {
perror("setsockopt (SO_BROADCAST)");
exit(1);
}
struct sockaddr_in bindaddr;
memset(&bindaddr, 0, sizeof(bindaddr));
bindaddr.sin_family = AF_INET;
bindaddr.sin_port = htons(MY_PORT);
bindaddr.sin_addr.s_addr = INADDR_ANY;
int yes=1;
if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes,
sizeof(yes)) == -1) {
perror("setsockopt (SO_REUSEADDR)");
exit(1);
}
if (bind(sockfd, (struct sockaddr *)&bindaddr, sizeof(bindaddr)) == -1) {
perror("bind");
exit(1);
}
broadcast = 1;
if (setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &broadcast,
sizeof broadcast) == -1) {
perror("setsockopt (SO_BROADCAST)");
exit(1);
}
struct sockaddr_in braddr;
memset(&braddr, 0, sizeof(braddr));
braddr.sin_family = AF_INET;
braddr.sin_port = htons(MY_PORT );
braddr.sin_addr.s_addr = INADDR_BROADCAST;
strncpy(buffer, "Hello world", sizeof(buffer));
char* ipString = inet_ntoa(bindaddr.sin_addr);
while(1){
printf("%s", ipString);
if (sendto(sockfd, buffer, sizeof(buffer), 0, (struct sockaddr *)&braddr, sizeof(braddr)) == -1){
perror("sendto");
exit(1);
}
peeraddr_len = sizeof(peeraddr);
}
return 0;
}