Added socket.io server to project.

server/.gitignore

@@ -0,0 +1,2 @@
+node_modules
+*.env

server/index.js

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+const dotenv = require("dotenv");
+const express = require("express");
+const http = require("http");
+const { Server } = require("socket.io");
+
+dotenv.config();
+const app = express();
+const server = http.createServer(app);
+const io = new Server(server);
+
+io.on("connection", (socket) => {
+
+    // Join a room.
+    socket.on("joinRoom", async (room) => {
+        try {
+            await socket.join(room);
+        } catch (error) {
+            console.error(`Error joining room: ${error}`);
+        }
+    });
+
+    // Broadcast the received message.
+    socket.on("message", async ({ room, message }) => {
+        try {
+            await socket.to(room).emit("message", message);
+        } catch (error) {
+            console.error(`Error broadcasting message: ${error}`);
+        }
+    });
+
+    socket.on("drawing-update", async ({ room, drawing }) => {
+        try {
+            await socket.to(room).emit("drawing-update", drawing);
+        } catch (error) {
+            console.error(`Error broadcasting drawing: ${error}`);
+        }
+    });
+
+    socket.on("disconnect", () => {
+        // console.log("user disconnected");
+    });
+});
+
+process.env.NODE_ENV !== "TEST"
+    ? server.listen(process.env.PORT, () => {
+          console.log(`Listening on ${process.env.PORT}`);
+      })
+    : null;
+
+module.exports = { server };
+