DRdrawkbox·Dec 29, 2016
True but you can create a reliable UDP implementation and get the same TCP features you need (resending/ordering/ACK). Many games use UDP and then some form of reliable UDP where important messages are ACK'd (game start, game end, global events etc).[1] Almost every multiplayer game I have worked on has a flavor of this, where there is a bit or flag on important messages that need reliable tracking over UDP. Everything else is just broadcast like player positions, local action and more where packets can be missed and extrapolated/interpolated, predictive methods and lag compensation.
There can also be some packet loss increase when using TCP mixed with UDP[2]. Most games built recently probably use more RUDP than TCP. But when you need to use any UDP at all you may as well just go reliable UDP. TCP definitely works for non-realtime game
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s and turn based especially but if you ever want some non essential systems updating where packet loss is ok (maybe world physics, or events that are just decorative/fun) then reliable UDP is best in my opinion.
SCTP was supposed to fix much of this but really reliable UDP does almost everything you need for realtime and not, so if investing in a network lib/tech that is the best choice.
enet[3] is a popular reliable UDP framework that was the base or basis for many others. RakNet[4] also has some nice implementations of it. There are many others now but some larger common systems based their systems on these, Unity is one.
[1] https://en.wikipedia.org/wiki/Reliable_User_Datagram_Protoco...
Characteristics of UDP Packet Loss: Effect of TCP Traffic
[2] http://www.isoc.org/INET97/proceedings/F3/F3_1.HTM
[3] http://enet.bespin.org/
[4] https://github.com/OculusVR/RakNet