Hi All,
I've found the solution and wanted to share it for future reference.
It turned out that the device which was sending the broadcast had a
different netmask than the receiving device.
This difference in netmask resulted in a wrong calculated broadcast ip.
Wire Shark displays this, because it simply displays everything on the wire.
The windows call stack also receives it, but drops it because it's send
to the wrong broadcast ip.
Thanks Angus for thinking with me!
Merijn
On 6/21/2010 16:53, Merijn Bosma wrote:
Hi All,
I'm currently at a customer site and I need to receive data sent with
UDP broadcast.
I've done this quite often without problems, but at the moment I have
a problem of which I'm not sure where to look.
(As always) I've set up my receiving socket like this:
fUDPServer := TWSocketServer.Create(nil);
fUDPServer.Proto := 'udp';
fUDPServer.Port := PORT;
fUDPServer.Addr := '0.0.0.0';
fUDPServer.OnDataAvailable := OnUDPDataAvailable;
fUDPServer.Listen();
I do not receive the data sent at all, I _do_ see the data with Wire
Shark.
After some testing (making a UDP broadcasting and listening client
self) I've found that I only receive UDP broadcasted messages sent to
255.255.255.255.
Unfortunately, the message I need to receive are sent to x.x.x.255
(only the last byte of the IP address is set to 255). I also see this
in Wire Shark.
If I sent a broadcast myself to 255.255.255.255 I receive it in my own
UDP listener, if I send it to x.x.x.255 I do not receive it in my own
listener.
Is there any way to receive this data using ICS or does anybody else
have a good tip in which direction to search?
Here a log line of Wire Shark in which you can see Wire Shark does
receive this data: 564 0.901067 10.68.112.66 10.68.112.255 UDP Source
port: 1120 Destination port: 1120
Kind regards,
Merijn
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