Server hanging on recvfrom() for UDP socket (C, Windows) - c

Question

I'm trying to receive some data from my client and my server appears to hang when it hits the recvfrom() function. I can't tell what's going wrong or if something is potentially wrong with my socket setup. I've coded this in Python too and it works fine and appears the sockets are setup the same. Below is the full code in question, with the hanging happening at the bottom. I'm new to C so apologies for any confusion or idiocy. Thanks so much in advance for any help.
#define _WINSOCK_DEPRECATED_NO_WARNINGS
#define WIN32_LEAN_AND_MEAN
#pragma comment (lib, "Ws2_32.lib")
#pragma comment (lib, "Mswsock.lib")
#pragma comment (lib, "AdvApi32.lib")
#include <winsock2.h>
#include <Ws2tcpip.h>
#include < ws2ipdef.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#define PORT 25678
#define STREAM "235.5.4.5"
int main(int argc, char* argv[]) {
int sockfd;
struct sockaddr_in sin, group;
int sin_len, done;
const int buffer_len = 1024;
char buffer[1024];
WSADATA wsaData;
printf("Initializing the winsock library ... ");
if (WSAStartup(MAKEWORD(1, 1), &wsaData) == SOCKET_ERROR) {
return -1;
}
memset(&sin, 0, sizeof(sin));
//1 create a socket
printf("Creating a socket ... ");
sockfd = socket(AF_INET, SOCK_DGRAM, 0);
if (sockfd == -1) { perror("Error opening socket"); exit(1); }
//2 set generic socket options
u_int share;
if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &share, sizeof(share)) < 0) {
perror("setsockopt"); exit(1);
}
//3 bind the socket to the port
sin.sin_family = AF_INET;
sin.sin_port = htons(PORT);
sin.sin_addr.s_addr = htonl(INADDR_ANY);
sin_len = sizeof(sin);
if (bind(sockfd, (struct sockaddr*)&sin, sin_len) < 0) {
exit(1);
};
//4 set up mreq
group.sin_family = AF_INET;
group.sin_port = htons(PORT);
group.sin_addr.s_addr = inet_addr(STREAM);
struct ip_mreq mreq;
mreq.imr_multiaddr = group.sin_addr;
mreq.imr_interface.s_addr = htonl(INADDR_ANY);
//5 set the socket options to the mreq
if (setsockopt(sockfd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0) {
printf("ERROR adding membership");
exit(1);
}
done = 0;
int nb;
//6 listen
while (!done) {
//int recvfrom(int socket, char *buf, int buflen, int flags, struct sockaddr* addr, int* addrlen);
nb = recvfrom(sockfd, (char*)buffer, buffer_len, 0, (struct sockaddr*)&sin, &sin_len);
}
close(sockfd);
return(0);
}