TCP and UDP occurring over the same route on a WAN can wreak havoc with UDP packet loss.[1] Using both is only a good idea up until you dig deep into socket performance. A network is not a piece of software where you can isolate things and expect them to behave in an isolated way, everything you push over it interacts with everything else that you are pushing over it. This "use UDP and TCP" is a dangerous anti-pattern because it seems to be an obvious solution from a software perspective, but is in reality a problem from the electron perspective. To paraphrase a famous quote:

> Some game developers, when confronted with a TCP problem, think "I know, I'll add UDP." Now they have two problems.

Games that implement their own protocol over UDP typically have packet modes (frequently a "channel" akin to WebSocket channels): reliable, ordered delivery or neither or either. There is almost always the notion of a connection, where appropriate. This is the correct way to do things, and with Raknet now being free you really have no excuse to do it any other way.

For authentication you could just use the reliable/ordered channel and carry on as though you were using TCP - which somewhat defeats the purpose of this article.

[1]: https://www.isoc.org/inet97/proceedings/F3/F3_1.HTM

With my example for login, my assumption was that one would use short-lived TCP connections (i.e. server receives login packet, sends success/fail and finally closes the connection), not a simultaneous, persistent connection where TCP congestion (and thus UDP packet loss) becomes an issue. But maybe I'm wrong on this one.

Thanks for sharing by the way, great article (although as an aside, some of those graphs are really hard to read).

> some of those graphs are really hard to read

I have to admit that I had to squint a bit while reading it myself.

I took it to mean that you might use UDP for doing stuff in game that might result in losing items. Like, I dunno, maybe an attacker on campus or on WiFi proxies your connection then makes you lose or drop expensive items.

I'm not sure how realistic a threat this is. Most likely crypto just helps obfuscate the game to make cheating/RE a bit harder.

When I used to play games like this the popular technique was to dos your connection, then just kill you and take your stuff while you're trying to reconnect.

This was pretty common in the early days of Ultima Online, since your character persisted for about three minutes after you logged out (unless you were in your house or an inn).

I don't understand - DTLS is covered in depth in the article (as are your or concerns)

> Sorry to nitpick but UDP seems like the wrong protocol for authentication.

While authentication over UDP is indeed a bit more difficult if implementing it yourself, fortunately there is DTLS which is a very official and well-recognised way to implement authentication over UDP (very briefly - DTLS does make a handshake, and it does have a session, but this session operates in a packet-oriented mode which supports reordering and packet loss).