Improve networking

server/game/game_server.ts

@@ -18,9 +18,10 @@ import {
 	CRAFTING_RESULT_SLOT,
 	MAX_CHAT_LENGTH,
 	MAX_NAME_LENGTH,
+	PROTOCOL_VERSION,
 	ServerMessage,
 } from "$/common/protocol.ts";
-import type { ModListing, RecipeBook } from "$/common/mod_loader.ts";
+import type { AtlasListing, ModListing, RecipeBook } from "$/common/mod_loader.ts";
 import type { WorldgenSetup } from "$/common/generation.ts";
 import { BLOCK_BEHAVIORS } from "./blocks.ts";
 import { ModRuntime, run_guarded } from "./mod_runtime.ts";
@@ -34,6 +35,8 @@ const EYE_HEIGHT = 1.69;
 // tiles further than this many chunks from every player don't tick
 const SIMULATION_DISTANCE = 6;
 const MAX_GIVE = 64 * 36;
+// how long a client gets between welcome and ready to download and load everything
+const READY_TIMEOUT_TICKS = 60 * TICKS_PER_SECOND;
 
 // everything the game server needs from whatever runs it
 export interface GameHost {
@@ -63,6 +66,7 @@ export interface SavedWorld {
 // the loaded mods, see load_mods.ts
 export interface GameMods {
 	listings: ModListing[];
+	atlas: AtlasListing;
 	recipes: RecipeBook;
 	worldgen?: WorldgenSetup;
 	runtime: ModRuntime;
@@ -72,6 +76,8 @@ export class GameServer {
 	world: ServerWorld;
 	#host: GameHost;
 	#players = new Map<number, ServerPlayer>();
+	// connections that got welcome and are downloading mods, by conn
+	#pending = new Map<number, { name: unknown; since: number }>();
 	#saved_players: Record<string, SavedPlayer> = {};
 	#tick = 0;
 	#mods: GameMods;
@@ -108,6 +114,7 @@ export class GameServer {
 	on_connect(_conn: number) {}
 
 	on_disconnect(conn: number) {
+		this.#pending.delete(conn);
 		const player = this.#players.get(conn);
 		if (!player) {
 			return;
@@ -135,9 +142,7 @@ export class GameServer {
 
 		const player = this.#players.get(conn);
 		if (!player) {
-			if (message.type === "hello") {
-				this.#join(conn, message.name);
-			}
+			this.#handshake(conn, message);
 			return;
 		}
 
@@ -182,6 +187,13 @@ export class GameServer {
 
 		this.mods.tick();
 
+		for (const [conn, pending] of this.#pending) {
+			if (this.#tick - pending.since > READY_TIMEOUT_TICKS) {
+				this.#pending.delete(conn);
+				this.#reject(conn, "Took too long to load the server's mods");
+			}
+		}
+
 		for (const player of this.#players.values()) {
 			this.#sync(player);
 		}
@@ -308,6 +320,52 @@ export class GameServer {
 
 	// messages
 
+	// hello -> welcome, then ready -> join. see "Delivery to clients" in MODS.md
+	#handshake(conn: number, message: ClientMessage) {
+		if (message.type === "hello") {
+			if (this.#pending.has(conn)) {
+				return;
+			}
+			if (message.protocol !== PROTOCOL_VERSION) {
+				this.#reject(
+					conn,
+					`This server needs a game version with protocol ${PROTOCOL_VERSION}, yours has ${
+						message.protocol ?? "none"
+					}. Reload the page to update.`,
+				);
+				return;
+			}
+			this.#pending.set(conn, { name: message.name, since: this.#tick });
+			this.#host.send(
+				conn,
+				JSON.stringify(
+					{
+						type: "welcome",
+						protocol: PROTOCOL_VERSION,
+						seed: this.world.seed,
+						atlas: this.#mods.atlas,
+						mods: this.#mods.listings,
+					} satisfies ServerMessage,
+				),
+			);
+			return;
+		}
+
+		if (message.type === "ready") {
+			const pending = this.#pending.get(conn);
+			if (!pending) {
+				return;
+			}
+			this.#pending.delete(conn);
+			this.#join(conn, pending.name);
+		}
+	}
+
+	#reject(conn: number, reason: string) {
+		this.#host.send(conn, JSON.stringify({ type: "rejected", reason } satisfies ServerMessage));
+		this.#host.close(conn);
+	}
+
 	#join(conn: number, raw_name: unknown) {
 		const player = new ServerPlayer(conn, this.#unique_name(raw_name));
 		const saved = this.#saved_players[player.name];
@@ -316,11 +374,9 @@ export class GameServer {
 		}
 
 		this.#send(player, {
-			type: "welcome",
+			type: "join",
 			id: player.id,
 			name: player.name,
-			seed: this.world.seed,
-			mods: this.#mods.listings,
 			players: [...this.#players.values()].map((p) => p.info()),
 			changes: this.world.all_changes(),
 			spawn: { x: player.x, y: player.y, z: player.z, yaw: player.yaw, pitch: player.pitch },