I am having trouble with UDP broadcast datagrams. I have a small VB6
test app that binds to 0.0.0.0 on port 6200. It sends a datagram to
"255.255.255.255" on port 6201. There is a second socket that is bound
to port 6201 on the same address. All computers receive this datagram
except for the computer which sent it. FYI the computer is running
Windows XP SP2 v.2149

If I run this same application on any other computer on the network
(even Windows Vista), the sending computer receives the datagram it
has broadcast, so the problem is confined to only one computer.

I have tried the same example in C# as well, so the problem is
definitely on a lower level. Just to be clear specifically sending to
the IP address of any interface on the machine does work and the
message is received, it just does not receive broadcast messages it
has sent itself. It also received broadcast messages sent from another
computer.

Incidentally, the problematic computer does receive its own broadcast
messages only while I am running Ethereal/Wireshark in packet
capturing mode. I have told that this is because Ethereal switches the
interface over to promiscuous mode. Indeed, coding the extra bit to
put the interface into promiscuous mode in my C# example does make the
example work.

I have disabled the network card and plugged in a Wifi adapter,
thinking it be the network causing the problem, but the results are
the same. Also, all the computers are running more or less the same
software and firewall(ZoneAlarm) so its not that either.

Why is only on this one computer that it doesn't work?