Linux UDP Broadcast minimal example

broadcast.c

#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <unistd.h>

int enable = 1;

int listener(int sock)
{
	printf("Listener\n");
	struct sockaddr_in rcv_addr = {};
	socklen_t addr_len = sizeof(rcv_addr);

	/* We bind it to broadcast addr on the given port */
	rcv_addr.sin_family = AF_INET;
	rcv_addr.sin_port = htons(6969);
	rcv_addr.sin_addr.s_addr = INADDR_ANY;

	if (bind(sock, (struct sockaddr *) &rcv_addr, sizeof(struct sockaddr_in)) < 0)
	{
		exit(1);
	}


	while(1)
	{
		char buf[128] = {};

		int len = recvfrom(sock, buf, sizeof(buf), 0, (struct sockaddr*)&rcv_addr, &addr_len);

		if (len <= 0) { continue; }

		printf(":%s\n", buf);
	}

	return 0;
}

int broadcaster(int sock)
{
	printf("Broadcaster\n");
	char hello[] = "Hello neighbor";

	while(1)
	{
		struct sockaddr_in name = {};
		name.sin_family = AF_INET;
		name.sin_port = htons(6969);
		name.sin_addr.s_addr = htonl(INADDR_BROADCAST);
		sendto(sock, hello, sizeof(hello), 0, (struct sockaddr*)&name, sizeof(name));
		sleep(1);
	}

	return 0;
}

int main(int argc, const char* argv[])
{
	int sock = socket(AF_INET, SOCK_DGRAM, 0);
	setsockopt(sock, SOL_SOCKET, SO_BROADCAST, (const void*)&enable, sizeof(enable));

	if (argc > 1)
	{
		return listener(sock);
	}
	else
	{
		return broadcaster(sock);
	}

	return 0;
}