UDP Sockets - One server, mulitple clients. Not sent to all clients - c

Question

I am writing in windows, using Visual Studio, and am trying to have one application use UDP sockets to broadcast a message to other applications. This must be done with UDP sockets.
It works well with just one client, but it does not when I add another client, and all listen on the same port.
TX (Server)
/* Example from: http://matrixsust.blogspot.com/2011/10/udp-server-client-in-c.html */
/* Use legacy sockets */
#define _WINSOCK_DEPRECATED_NO_WARNINGS
/* Add a linker to ws2_32.lib, the Winsock2 library */
#pragma comment(lib, "ws2_32.lib")
#include <stdio.h>
#include <winsock2.h>
int main()
{
WSADATA wsaData;
int sock, sin_size;
struct sockaddr_in server_addr;
struct hostent* host;
char send_data[1024];
boolean keep_running = 1;
unsigned int cmd_no_block_arg = 1;
int SERVER_PORT;
/* Obtain a valid port */
printf("Enter a port number to connect to (i.e. 7171):\n");
scanf_s("%d", &SERVER_PORT);
if ((SERVER_PORT < 1) || (SERVER_PORT > 665534))
{
SERVER_PORT = 7171;
}
/* Initialize Winsock version 2.2 */
WSAStartup(MAKEWORD(2, 2), &wsaData);
/* CLIENT SIDE */
host = (struct hostent*) gethostbyname((char*)"127.0.0.1");
if ((sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1)
{
perror("socket");
exit(1);
}
/* SETUP */
server_addr.sin_family = AF_INET;
server_addr.sin_port = htons(SERVER_PORT);
server_addr.sin_addr = *((struct in_addr*)host->h_addr);
memset(server_addr.sin_zero, 0, sizeof(server_addr.sin_zero));
sin_size = sizeof(struct sockaddr);
/* Bind the socket, then enable non-blocking semantics */
if ((ioctlsocket(sock, FIONBIO, &cmd_no_block_arg) == SOCKET_ERROR))
{
printf("Could not non-bind socket. Error Code %i\n", WSAGetLastError());
}
while (keep_running)
{
printf("Type Something (q or Q to quit):");
gets_s(send_data, sizeof(send_data));
if ((strcmp(send_data, "q") == 0) || strcmp(send_data, "Q") == 0)
{
keep_running = 0;
}
else
{
sendto(sock, send_data, strlen(send_data), 0, (struct sockaddr*) & server_addr, sizeof(struct sockaddr));
}
} // While
}
RX (Clients)
/* Example from: http://matrixsust.blogspot.com/2011/10/udp-server-client-in-c.html */
#define _WINSOCK_DEPRECATED_NO_WARNINGS
/* Add a linker to ws2_32.lib, the Winsock2 library */
#pragma comment(lib, "ws2_32.lib")
#include <stdio.h>
#include <winsock2.h>
#include <sys/types.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
int main()
{
WSADATA wsaData;
int sock;
int addr_len, bytes_read;
char recv_data[1024], send_data[1024];
struct sockaddr_in server_addr, client_addr;
int sharing_flag = 1; /* Allow sharing */
unsigned int non_block_flag = 1;
unsigned int SERVER_PORT = 7171;
/* Obtain a valid port to connect to */
printf("Enter a port number to connect to (i.e. 7171):\n");
scanf_s("%d", &SERVER_PORT);
if ((SERVER_PORT < 1) || (SERVER_PORT > 65535))
{
SERVER_PORT = 7171;
}
/* Initialize Winsock version 2.2 */
WSAStartup(MAKEWORD(2, 2), &wsaData);
/* SERVER SIDE: bind(), recvfrom(), sendto() */
if ((sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1) {
perror("Socket");
exit(1);
}
server_addr.sin_family = AF_INET;
server_addr.sin_port = htons(SERVER_PORT);
server_addr.sin_addr.s_addr = INADDR_ANY;
memset(server_addr.sin_zero, 0, sizeof(server_addr.sin_zero));
/* Eliminates "ERROR on binding: Address already in use" error */
if (setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (void*)&sharing_flag, sizeof(sharing_flag)) == SOCKET_ERROR)
{
printf("Error on socket opt: %i\n", WSAGetLastError());
}
if ((bind(sock, (struct sockaddr*) & server_addr, sizeof(struct sockaddr)) == SOCKET_ERROR) ||
(ioctlsocket(sock, FIONBIO, &non_block_flag) == SOCKET_ERROR))
{
printf("Error on socket bind: %i\n", WSAGetLastError());
}
addr_len = sizeof(struct sockaddr);
printf("\nUDPServer Waiting for client on port %i\n", SERVER_PORT);
while (1)
{
bytes_read = recvfrom(sock, recv_data, 1024, 0, (struct sockaddr*) & client_addr, &addr_len);
if (bytes_read >= 0)
{
recv_data[bytes_read] = '\0';
printf("\n(%s , %d) said : ", inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port));
printf("%s\n", recv_data);
fflush(stdout);
} /* if we read in bytes */
} /* while */
return 0;
}