The game allready use UDP only for multiplayer. They only remove the interconnection between player and placing the authority ( validation of action ) to only one place ( server ) instead of having everyone to validate every action.PacifyerGrey wrote: To network "masters"
If you are trying to suggest using UDP you probably never developed any client-server apps. While when applying UDP to VoIP or streams you can accept packet loss even if it is severe, in games like Factorio data loss is not acceptable at all so TCP is the only valid option.
UDP can be used in multiplayer games only in case that you do transmit the full game state in every data chunk so if you dropped a chunk due to packet loss you might catch up when you recieve next chunk. This might apply to shooters for example when the map is static and all data you transfer from server is updated positions of players/projectiles. In Factorio only player actions are transmitted so dropping an action will surely result in a different game state on two ends.
In the end the choice of protocol depend on what you really need and how you are able to hide the latency.
TCP : you need 100% reliability of data but didn't care that much of the speed. ( ex : card game )
UDP : you need speed but didn't care that much about reliability. ( ex : realtime game )
You can't have both.
With the next factorio multiplayer the server will be the only one who have the "real" state of the game. So every player will adjust their game state to the server so you'll not have different game state on two ends.