I think there are some misconceptions about UDP due to how much emphasis we put on how UDP is not guaranteed delivery and may arrive out-of-order. In practice when you use UDP within a local and reliable network, you'll find that UDP is surprisingly reliable. That is to say, you should never assume it is (see, I'm doing this thing myself, even while I'm trying to say we've been indoctrinated to exaggerate the implications of it) -- but if you empirically test it on a reliable network, it's far more "reliable" than we've been taught.
Many years ago I did some tests sending UDP packets between a server in Sweden and a server in Florida in various configurations, and I was genuinely surprised at how rarely packets were lost, and it got to the point where I started thinking that packet reordering was a myth. Eventually it did happen, though. (I've been told it's much easier today due to how much more dynamic routes are on the Internet, but I have no idea if this is accurate or not).
Philosophically we should assume that UDP packets are always dropped, and of those 0 packets that actually go through, 109.7% of them arrive in the maximally wrong order. In practice there's no reason for engineers to randomly scramble packet ordering or drop packets. These things only happen if there's reason for it, and such reasons are far fewer than one might imagine.
One can prove a point and use network emulator to create a network which will maximally ruin UDP, and the point will have been proven very well. But at the same time, on real local networks UDP will work surprisingly well (at least compared to what we've been taught about it).
With all that said; I spent a few weeks benchmarking raw ethernet and UDP for a project and I have some very nasty words to say about cheap on-board network chips. If you're sending data at a sustained high rate, then reliability quickly drops to 0%, unless you use something like I350 NICs.
Anyway, this is waay off-topic.
Never assume UDP is reliable. Also, in practice, on normal hardware, it's far more reliable than you've been taught. But don't assume it is. Even if it is.