Simple Windows 10 UDP Broadcast Send and Receive Not Working - c++

Question

I am trying to implement a simple UDP broadcaster and listener on two PCs running Windows 10 64 Pro (1803). I have come across numerous c/c++ examples but I cannot get any of them to work on my local net.
I set up a receiver PC on my local net at 192.168.0.1 and a sender PC at 192.168.0.2 with subnet masks 255.255.255.0 and use the local broadcast address of 192.168.0.255.
They do work when used on the same machine with localhost, MS loopback adapter and any local adapter I might choose. They also work with two machines connected to a wifi router with a gateway. They just don't seem to work with a regular basic switch, which is what I need. I can see the messages coming in on the listener PC using Wireshark but my listener code (recvfrom()) does not respond. If tried disabling the Windows firewall but that has no effect.
*One interesting thing. If I have the listener code up, and send a broadcast from that listener PC, the listener code WILL respond to that and to subsequent broadcasts from the broadcaster PC while in the while loop. If I exit and restart, its the same nonresponsive result as before.*
This code that follows is one of many I have tried but they're all basically the same handful of operations.
Example sender code:
#include <winsock2.h>
#include <iostream>
#include <conio.h>
using namespace std;
#define MYPORT 9009 // the port users will be connecting to
int main()
{
WSADATA wsaData;
WSAStartup( MAKEWORD( 2, 2 ), &wsaData );
SOCKET sock;
sock = socket( AF_INET, SOCK_DGRAM, 0 );
char broadcast = '1';
if ( setsockopt( sock, SOL_SOCKET, SO_BROADCAST, &broadcast, sizeof(broadcast) ) < 0 )
{
cout<<"Error in setting Broadcast option";
closesocket(sock);
return 0;
}
struct sockaddr_in Recv_addr;
struct sockaddr_in Sender_addr;
int len = sizeof( struct sockaddr_in );
char sendMSG[] ="Attention: this is a broadcast!!!";
char recvbuff[50] = "";
int recvbufflen = 50;
Recv_addr.sin_family = AF_INET;
Recv_addr.sin_port = htons( MYPORT );
Recv_addr.sin_addr.s_addr = inet_addr( "192.168.0.255" ); // switch doesnt work
// Recv_addr.sin_addr.s_addr = inet_addr( "192.168.1.255" ); //wifi router works
cout << "sending message: " << sendMSG;
sendto( sock, sendMSG, (int) strlen(sendMSG)+1, 0,(sockaddr*) &Recv_addr, sizeof( Recv_addr ) );
closesocket( sock );
WSACleanup();
}
Example receiver code:
#include "winsock2.h"
#include <iostream>
#include <conio.h>
using namespace std;
#define MYPORT 9009 // the port users will be connecting to
int main()
{
WSADATA wsaData;
WSAStartup( MAKEWORD( 2, 2 ), &wsaData );
SOCKET sock;
sock = socket( AF_INET, SOCK_DGRAM, 0 );
char broadcast = '1';
// This option is needed on the socket in order to be able to receive broadcast messages
// If not set the receiver will not receive broadcast messages in the local network.
if ( setsockopt( sock, SOL_SOCKET, SO_BROADCAST, &broadcast, sizeof( broadcast ) ) < 0 )
{
cout<<"Error in setting Broadcast option";
closesocket(sock);
return 0;
}
struct sockaddr_in Recv_addr;
struct sockaddr_in Sender_addr;
int len = sizeof( struct sockaddr_in );
char recvbuff[50];
int recvbufflen = 50;
Recv_addr.sin_family = AF_INET;
Recv_addr.sin_port = htons( MYPORT );
Recv_addr.sin_addr.s_addr = INADDR_ANY;
if ( bind( sock, (sockaddr*) &Recv_addr, sizeof (Recv_addr) ) < 0 )
{
cout << "Error in BINDING" << WSAGetLastError();
_getch();
closesocket(sock);
return 0;
}
do
{
cout << "\nWaiting for message...\n";
recvfrom( sock, recvbuff, recvbufflen, 0, (sockaddr*) &Sender_addr, &len );
cout << "Received Message is: " << recvbuff;
} while ( 1 );
closesocket(sock);
WSACleanup();
}