@jnm2 makes a good point. The endPacket problem/feature/bug and buffering for sending could and should be fixed. I would attempt to fix it if I was proficient enough in c++.
Good Luck! Personally I have abandoned the spark core for receiving UDP packets. I can't design something that doesn't follow network standards. Even if I could tell 3rd parties that I needed them to encapsulate their UDP packets in an envelope they would laugh. Nor do they want to spend the development time implementing. I also refuse to write a UDP proxy either, one of the many points of UDP is the speed and this takes away from the speed. I also don't want to have to additionally support a proxy increasing my total cost ownership.
I hope from all the threads about UDP that the photon addresses all these problems. I really like the "spark" feature set: cloud, web ide, community, price, ability to use wifi without much difficulty, and all the other features. Nice job spark team. Please have this fixed in the photon.
Thanks