Create Index.js

Index.js

@@ -0,0 +1,12 @@
+npm install express ws
+const { createHttpServer } = require("./src/server/httpServer");
+const { createWSServer } = require("./src/server/wsServer");
+
+const server = createHttpServer();
+createWSServer(server);
+
+const PORT = process.env.PORT || 3000;
+
+server.listen(PORT, () => {
+    console.log(`Multiplayer backend running on port ${PORT}`);
+});

app.js

@@ -0,0 +1,33 @@
+const express = require("express");
+const http = require("http");
+const WebSocket = require("ws");
+const { handleEvent } = require("./game");
+
+const app = express();
+app.use(express.json());
+
+// HTTP test route
+app.get("/health", (req, res) => {
+    res.json({ status: "ok" });
+});
+
+// create server
+const server = http.createServer(app);
+
+// websocket layer
+const wss = new WebSocket.Server({ server });
+
+wss.on("connection", (ws) => {
+    ws.on("message", (msg) => {
+        try {
+            const event = JSON.parse(msg);
+            handleEvent(event, ws, wss);
+        } catch (e) {
+            console.log("bad message");
+        }
+    });
+
+    ws.send(JSON.stringify({ type: "welcome" }));
+});
+
+module.exports = server;

game.js

@@ -0,0 +1,48 @@
+const gameState = {
+    players: {},
+    status: "waiting"
+};
+
+function handleEvent(event, ws, wss) {
+
+    if (event.type === "join") {
+        gameState.players[event.playerId] = {
+            id: event.playerId,
+            x: 0,
+            y: 0
+        };
+
+        ws.send(JSON.stringify({
+            type: "joined",
+            state: gameState
+        }));
+    }
+
+    if (event.type === "move") {
+        const p = gameState.players[event.playerId];
+        if (!p) return;
+
+        p.x = event.x;
+        p.y = event.y;
+
+        broadcast(wss);
+    }
+
+    if (event.type === "start") {
+        gameState.status = "live";
+        broadcast(wss);
+    }
+}
+
+function broadcast(wss) {
+    wss.clients.forEach(c => {
+        if (c.readyState === 1) {
+            c.send(JSON.stringify({
+                type: "state",
+                state: gameState
+            }));
+        }
+    });
+}
+
+module.exports = { handleEvent };