diff --git a/deno.lock b/deno.lock
index 7b2008d..2cadff8 100644
--- a/deno.lock
+++ b/deno.lock
@@ -2,6 +2,7 @@
   "version": "5",
   "specifiers": {
     "jsr:@std/assert@*": "1.0.19",
+    "jsr:@std/http@*": "1.1.3",
     "jsr:@std/internal@^1.0.12": "1.0.14"
   },
   "jsr": {
@@ -11,6 +12,9 @@
         "jsr:@std/internal"
       ]
     },
+    "@std/http@1.1.3": {
+      "integrity": "73a98e05ff58aa18bea562d286172e6c815b1eddd4fcab194beda19e3683b88c"
+    },
     "@std/internal@1.0.14": {
       "integrity": "291516b3d4c35024d6ffbc0a9df5bf4c64116e05b50012cf846710152d2ffdf7"
     }
diff --git a/engine/lib/assertNever.ts b/engine/lib/assertNever.ts
new file mode 100644
index 0000000..dd4d548
--- /dev/null
+++ b/engine/lib/assertNever.ts
@@ -0,0 +1,3 @@
+export function assertNever(): never {
+	throw new Error("never");
+}
diff --git a/server/client.test.ts b/server/client.test.ts
index ae7e99b..88d5dce 100644
--- a/server/client.test.ts
+++ b/server/client.test.ts
@@ -1,107 +1,14 @@
 /// <reference lib="deno.ns" />
 import { assertEquals } from "jsr:@std/assert";
-import { startServer } from "./deno.ts";
-
-const hostname = "0.0.0.0";
-const port = 8042;
-const href = `ws://${hostname}:${port}`;
-
-function connect(url: string): Promise<[WebSocket, string[]]> {
-	return new Promise((resolve, reject) => {
-		const messages: string[] = [];
-		const socket = new WebSocket(url);
-
-		socket.onopen = () => resolve([socket, messages]);
-		socket.onerror = (error) => reject(error);
-		socket.onmessage = ({ data }) => {
-			messages.push(data);
-		};
-	});
-}
-
-function close(socket: WebSocket): Promise<void> {
-	return new Promise((resolve) => {
-		if (socket.readyState === WebSocket.CLOSED) {
-			return resolve();
-		}
-		socket.onclose = () => resolve();
-		socket.close();
-	});
-}
-
-function setup(
-	fn: (ctx: Deno.TestContext) => Promise<void>,
-): (ctx: Deno.TestContext) => Promise<void> {
-	return async (ctx) => {
-		const shutdown = startServer(hostname, port);
-		try {
-			await fn(ctx);
-		} finally {
-			await shutdown();
-		}
-	};
-}
-
-function flush(): Promise<void> {
-	return new Promise((resolve) => setTimeout(resolve, 0));
-}
+import handler from "./handler.ts";
+import { close, connect, flush, href, setup } from "./testSetup.ts";
 
 Deno.test(
-	"Welcome all clients on connect.",
+	"test",
 	setup(async () => {
 		const [s1, m1] = await connect(href);
-		const [s2, m2] = await connect(href);
-
 		await flush();
-
-		assertEquals(m1, ["Welcome 1, type /join <room>."]);
-		assertEquals(m2, ["Welcome 2, type /join <room>."]);
-
-		await close(s2);
+		assertEquals(m1, []);
 		await close(s1);
-	}),
-);
-
-Deno.test(
-	"Messages all clients in a room on joining.",
-	setup(async () => {
-		const [s1, m1] = await connect(href);
-		const [s2, m2] = await connect(href);
-
-		await flush();
-		m1.length = 0;
-		m2.length = 0;
-
-		s1.send("/join meh");
-		s2.send("/join meh");
-		await flush();
-
-		assertEquals(m1, ["1 has joined!", "2 has joined!"]);
-		assertEquals(m2, ["2 has joined!"]);
-
-		await close(s2);
-		await close(s1);
-	}),
-);
-
-Deno.test(
-	"Messages remaining members if one left the room.",
-	setup(async () => {
-		const [s1, m1] = await connect(href);
-		const [s2, m2] = await connect(href);
-
-		s1.send("/join meh");
-		s2.send("/join meh");
-		await flush();
-
-		m1.length = 0;
-		m2.length = 0;
-		await close(s2);
-		await flush();
-
-		assertEquals(m1, ["2 has left!"]);
-		assertEquals(m2, []);
-
-		await close(s1);
-	}),
+	}, handler),
 );
diff --git a/server/handler.ts b/server/handler.ts
new file mode 100644
index 0000000..793b036
--- /dev/null
+++ b/server/handler.ts
@@ -0,0 +1,21 @@
+import { getCookies } from "jsr:@std/http/cookie";
+
+function getSessionId(request: Request): null | string {
+	getCookies(request.headers);
+	return null;
+}
+
+export default function (request: Request): Response {
+	if (request.headers.get("upgrade") !== "websocket") {
+		return new Response("Upgrade required.", { status: 426 });
+	}
+
+	const sessonId = getSessionId(request);
+	if (!sessonId) {
+		return new Response("Session requierd.", { status: 401 });
+	}
+
+	const { socket, response } = Deno.upgradeWebSocket(request);
+
+	return response;
+}
diff --git a/server/main.ts b/server/main.ts
index 8c2e840..8796ee3 100644
--- a/server/main.ts
+++ b/server/main.ts
@@ -1,3 +1,4 @@
-import { startServer } from "./deno.ts";
+import handler from "./handler.ts";
+import { startServer } from "./server.ts";
 
-startServer();
+startServer(handler);
diff --git a/server/ref/deno.test.ts b/server/ref/deno.test.ts
new file mode 100644
index 0000000..2292d19
--- /dev/null
+++ b/server/ref/deno.test.ts
@@ -0,0 +1,64 @@
+/// <reference lib="deno.ns" />
+import { assertEquals } from "jsr:@std/assert";
+import { close, connect, flush, href, setup } from "../testSetup.ts";
+import { getHandler } from "./deno.ts";
+
+Deno.test(
+	"Welcome all clients on connect.",
+	setup(async () => {
+		const [s1, m1] = await connect(href);
+		const [s2, m2] = await connect(href);
+
+		await flush();
+
+		assertEquals(m1, ["Welcome 1, type /join <room>."]);
+		assertEquals(m2, ["Welcome 2, type /join <room>."]);
+
+		await close(s2);
+		await close(s1);
+	}, getHandler()),
+);
+
+Deno.test(
+	"Messages all clients in a room on joining.",
+	setup(async () => {
+		const [s1, m1] = await connect(href);
+		const [s2, m2] = await connect(href);
+
+		await flush();
+		m1.length = 0;
+		m2.length = 0;
+
+		s1.send("/join meh");
+		s2.send("/join meh");
+		await flush();
+
+		assertEquals(m1, ["1 has joined!", "2 has joined!"]);
+		assertEquals(m2, ["2 has joined!"]);
+
+		await close(s2);
+		await close(s1);
+	}, getHandler()),
+);
+
+Deno.test(
+	"Messages remaining members if one left the room.",
+	setup(async () => {
+		const [s1, m1] = await connect(href);
+		const [s2, m2] = await connect(href);
+
+		s1.send("/join meh");
+		s2.send("/join meh");
+		await flush();
+
+		m1.length = 0;
+		m2.length = 0;
+		await close(s2);
+		await flush();
+
+		assertEquals(m1, ["2 has left!"]);
+		assertEquals(m2, []);
+
+		await close(s1);
+	}, getHandler()),
+);
diff --git a/server/deno.ts b/server/ref/deno.ts
similarity index 75%
rename from server/deno.ts
rename to server/ref/deno.ts
index 38df654..5695eb4 100644
--- a/server/deno.ts
+++ b/server/ref/deno.ts
@@ -1,9 +1,6 @@
 /// <reference lib="deno.ns" />
 
-export function startServer(
-	hostname: string = "localhost",
-	port: number = 8042,
-): () => Promise<void> {
+export function getHandler(): Deno.ServeHandler {
 	let nextId = 1;
 
 	const clientsMap = new Map<number, WebSocket>();
@@ -70,23 +67,14 @@ export function startServer(
 		socket.onerror = console.error;
 	};
 
-	const ac = new AbortController();
-	const server = Deno.serve(
-		{ hostname, port, signal: ac.signal },
-		(request) => {
-			if (request.headers.get("upgrade") !== "websocket") {
-				return new Response("Upgrade Required", { status: 426 });
-			}
+	return (request) => {
+		if (request.headers.get("upgrade") !== "websocket") {
+			return new Response("Upgrade Required", { status: 426 });
+		}
 
-			const { socket, response } = Deno.upgradeWebSocket(request);
-			handleConnection(socket);
+		const { socket, response } = Deno.upgradeWebSocket(request);
+		handleConnection(socket);
 
-			return response;
-		},
-	);
-
-	return () => {
-		ac.abort();
-		return server.finished;
+		return response;
 	};
 }
diff --git a/server/server.ts b/server/server.ts
new file mode 100644
index 0000000..733d9f2
--- /dev/null
+++ b/server/server.ts
@@ -0,0 +1,15 @@
+/// <reference lib="deno.ns" />
+
+export function startServer(
+	handler: Deno.ServeHandler,
+	hostname: string = "localhost",
+	port: number = 8042,
+): () => Promise<void> {
+	const ac = new AbortController();
+	const server = Deno.serve({ hostname, port, signal: ac.signal }, handler);
+
+	return () => {
+		ac.abort();
+		return server.finished;
+	};
+}
diff --git a/server/testSetup.ts b/server/testSetup.ts
new file mode 100644
index 0000000..8c11808
--- /dev/null
+++ b/server/testSetup.ts
@@ -0,0 +1,46 @@
+import { startServer } from "./server.ts";
+
+export const hostname = "0.0.0.0";
+export const port = 8042;
+export const href = `ws://${hostname}:${port}`;
+
+export function setup(
+	fn: (ctx: Deno.TestContext) => Promise<void>,
+	handler: Deno.ServeHandler,
+): (ctx: Deno.TestContext) => Promise<void> {
+	return async (ctx) => {
+		const shutdown = startServer(handler, hostname, port);
+		try {
+			await fn(ctx);
+		} finally {
+			await shutdown();
+		}
+	};
+}
+
+export function connect(url: string): Promise<[WebSocket, string[]]> {
+	return new Promise((resolve, reject) => {
+		const messages: string[] = [];
+		const socket = new WebSocket(url);
+
+		socket.onopen = () => resolve([socket, messages]);
+		socket.onerror = (error) => reject(error);
+		socket.onmessage = ({ data }) => {
+			messages.push(data);
+		};
+	});
+}
+
+export function close(socket: WebSocket): Promise<void> {
+	return new Promise((resolve) => {
+		if (socket.readyState === WebSocket.CLOSED) {
+			return resolve();
+		}
+		socket.onclose = () => resolve();
+		socket.close();
+	});
+}
+
+export function flush(): Promise<void> {
+	return new Promise((resolve) => setTimeout(resolve, 0));
+}