UDP flood/directed broadcaste question

Hi

I'm getting really confused. Having thought I understood the whole flood
broadcast/directed broadcast address situation and using 192.168.255.255 as
a directed broadcast address for my network, I now find that seemingly I can
use any address and it still works, yes I mean any address..... Because a
friend wanted my Delphi program and it didn't work, I tried using option
buttons to
allow the user to broadcast to different address,by changing the host
parameter, using the code:
UDPClient.host:='address'
each option button has a different address ie
    option button1 click did
    UDPClient.host:='192.168.255.255'
    option button2 click did
    UDPClient.host:='192.168.1.255'
    and so on and to test I had
    option button4 click did
    UDPClient.host:='300.168.255.255'

The last address was meant not to work, so I could test whether the host
address was really being changed.... but they all worked fine.

What is more confusing is that my subnet is 255.255.252.0 which I thought
would suggest a directed broadcast address of 192.168.3.255.

Can anyone shed some light on this for me?

Many thanks
Dave