UDP Broadcast using the CCS Ethernet development board

[Greg Richter]

Nice piece of code, with a little gotcha for UDP broadcast in UDP.C round about line 165:

// If remoteNode is supplied, remember it.
if ( remoteNode )
{
memcpy((void*)&p->remoteNode,
(void*)remoteNode,
sizeof(p->remoteNode));
}
// else Set broadcast address - TO BE DONE */

Oh, bother ... You can either modify the library code, or simply put:

RemoteNode.MACAddr.v[0] = 0xFF; // remote broadcast node
RemoteNode.MACAddr.v[1] = 0xFF;
RemoteNode.MACAddr.v[2] = 0xFF;
RemoteNode.MACAddr.v[3] = 0xFF;
RemoteNode.MACAddr.v[4] = 0xFF;
RemoteNode.MACAddr.v[5] = 0xFF;

RemoteNode.IPAddr.v[0] = 255;
RemoteNode.IPAddr.v[1] = 255;
RemoteNode.IPAddr.v[2] = 255;
RemoteNode.IPAddr.v[3] = 255;

... in your code to enable UDP broadcast. Truly a minor tweak, but it chewed up half a day chasing it down. If you're doing UDP broadcast with this library, this'll save you some time. Works beautifully, now.

-Greg
_________________
Madness takes it toll; please have exact change.

[asmallri]

The MAC address is fine. The IP layer address broadcast may or may not work depending on the stack implementation of the intended remote node. It also will not transit a router. A subnet broadcast can be used instead.

Let's say your target is on on subnet 192.168.1.0 with a mask of 255.255.255.0 then the broadcast address for the subnet is 192.168.1.255 - you can reach this from the local subnet or from behind a router.
_________________
Regards, Andrew

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