How to broadcast UDP message to 255.255.255.255

Digi TransPort WR (Series)
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1

I can send a broadcast using 192.168.10.255 port 7001. All receivers pick up the message fine.

But if I try send to 255.255.255.255 (or -1L) port 7001, nothing seems to transmit.

But, the rabbit receives UDP packets addressed to -1L Port 7000 just fine from Window machines on other subnets.

Code snippet:
//----------

udp_Socket sock;
udp_extopen(&sock,IF_ANY, LOCAL_PORT, -1L, 0, ReceiveHandlerFun, 0,0);

//Doesn’t send to anywhere: ** HELP, Why not??? **
udp_sendto(&sock,“helloWorld”,sizeof(“helloWorld”),-1L,7001)

//Sends ok to local subnet:
udp_sendto(&sock,“helloSubnet”,sizeof(“helloSubnet”),aton(“192.168.10.255”),7001)

//----------

2

Solved:
I had to change the interface from “IF_ANY” to “IF_ETH0”.

From:
udp_extopen(&sock,IF_ANY, LOCAL_PORT, -1L, 0, ReceiveHandlerFun, 0,0);

To:
udp_extopen(&sock,IF_ETH0, LOCAL_PORT, -1L, 0, ReceiveHandlerFun, 0,0);

Now it broadcasts UDP messages to -1L or 255.255.255.255.