B4A doesn't know if there are any B4ABridge devices out there until it does a ping (which B4Abridge devices would then respond to), so it will probably keep doing these pings to keep "looking" for B4Abridge devices on a continuous basis (even if you are currently not using B4ABridge) so it can quickly "find" any new B4Abridge devices if/when you eventually hook one up.
As you noticed its a UDP packet not a TCP, so it's probably a very small packet and is probably limited to the local network (doesn't go out on the internet). So, it should be nothing to worry about.