P2P Networking

[zicklag]

Convert's game to use GGRS for rollback networking instead of the client/server model. This also came with a lot of changes in various places, discovered while working on the rollback support:

• The matchmaker is now game agnostic and responsible for:
  • Matchmaking: aka. connecting peers to each other:
    • Clients may connect to the matchmaking server and ask to find a match with n other clients.
    • Clients must also specify an arbitrary byte-sequence for the match data, used as a filter so the client will only be connected to other clients with the same match data.
      • This allows for matching on game+mode combinations.
  • Proxying: Forwarding peer messages to the other peers
    • This overcomes several challenges with true peer-to-peer models, such as players knowing each-other's IP addresses and firewall hole punching issues.
• The TypeScript scripting engine is temporarily disabled.
  • With need to run up to 8 frames in a single 16ms update, the scripts couldn't run fast enough to use them for all the game logic.
  • Future optimizations to the scripting engine might allow the scripts to be re-enabled for network games.
  • While it's temporarily disabled, even if scripts are not fast enough for mutliplayer games we could enable them for local games for modding.
• Decorations still have to be migrated from the scripts to Rust
• There are a couple known bugs:
  • You can grab swords out of people's hands, sometimes from the position the sword was last dropped, even if the other player is across the map.
  • There was one big desync in a 3-player match. We have to track down the non-determinism that might have caused it. It is probably related to non-deterministic query iteration order somewhere.