diff --git a/app/__init__.py b/app/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/app/main.py b/app/main.py
new file mode 100644
index 0000000..af50af7
--- /dev/null
+++ b/app/main.py
@@ -0,0 +1,36 @@
+from pathlib import Path
+
+from fastapi import FastAPI
+from fastapi.responses import FileResponse
+from fastapi.staticfiles import StaticFiles
+
+from app.websocket.chat import router as chat_router
+from app.websocket.manager import manager
+
+BASE_DIR = Path(__file__).resolve().parent
+STATIC_DIR = BASE_DIR / "static"
+
+app = FastAPI(title="Simple WebSocket Chatroom")
+
+# WebSocket route: ws://localhost:8000/ws/{room_id}/{client_id}
+app.include_router(chat_router)
+
+# Frontend files
+app.mount("/static", StaticFiles(directory=STATIC_DIR), name="static")
+
+
+@app.get("/")
+async def home():
+    """Serve the chatroom GUI."""
+    return FileResponse(STATIC_DIR / "index.html")
+
+
+@app.get("/api/rooms")
+async def rooms():
+    """Small helper endpoint for the GUI/debugging."""
+    return manager.rooms_overview()
+
+
+@app.get("/health")
+async def health():
+    return {"status": "ok", "app": "Simple WebSocket Chatroom"}
diff --git a/app/websocket/__init__.py b/app/websocket/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/app/websocket/chat.py b/app/websocket/chat.py
new file mode 100644
index 0000000..882d974
--- /dev/null
+++ b/app/websocket/chat.py
@@ -0,0 +1,87 @@
+import json
+from datetime import datetime, timezone
+
+from fastapi import APIRouter, WebSocket, WebSocketDisconnect
+
+from app.websocket.manager import manager
+
+router = APIRouter()
+
+
+def now_iso() -> str:
+    return datetime.now(timezone.utc).isoformat()
+
+
+def event(event_type: str, room_id: str, client_id: str, content: str):
+    return {
+        "type": event_type,
+        "room_id": room_id,
+        "client_id": client_id,
+        "content": content,
+        "timestamp": now_iso(),
+    }
+
+
+def clean_value(value: str, fallback: str) -> str:
+    value = value.strip()
+    return value if value else fallback
+
+
+@router.websocket("/ws/{room_id}/{client_id}")
+async def websocket_endpoint(websocket: WebSocket, room_id: str, client_id: str):
+    room_id = clean_value(room_id, "عمومی")
+    client_id = clean_value(client_id, "ناشناس")
+
+    await manager.connect(websocket, room_id, client_id)
+
+    await manager.broadcast_json(
+        event("system", room_id, "سیستم", f"{client_id} وارد اتاق {room_id} شد."),
+        room_id,
+    )
+    await manager.broadcast_json(
+        {
+            "type": "presence",
+            "room_id": room_id,
+            "client_id": "سیستم",
+            "content": "presence-updated",
+            "users": manager.room_users(room_id),
+            "timestamp": now_iso(),
+        },
+        room_id,
+    )
+
+    try:
+        while True:
+            raw_data = await websocket.receive_text()
+
+            try:
+                data = json.loads(raw_data)
+                message = str(data.get("content", "")).strip()
+            except json.JSONDecodeError:
+                message = raw_data.strip()
+
+            if not message:
+                continue
+
+            await manager.broadcast_json(
+                event("message", room_id, client_id, message),
+                room_id,
+            )
+
+    except WebSocketDisconnect:
+        manager.disconnect(websocket, room_id)
+        await manager.broadcast_json(
+            event("system", room_id, "سیستم", f"{client_id} از اتاق {room_id} خارج شد."),
+            room_id,
+        )
+        await manager.broadcast_json(
+            {
+                "type": "presence",
+                "room_id": room_id,
+                "client_id": "سیستم",
+                "content": "presence-updated",
+                "users": manager.room_users(room_id),
+                "timestamp": now_iso(),
+            },
+            room_id,
+        )
diff --git a/app/websocket/manager.py b/app/websocket/manager.py
new file mode 100644
index 0000000..36a523b
--- /dev/null
+++ b/app/websocket/manager.py
@@ -0,0 +1,74 @@
+from dataclasses import dataclass
+from typing import Any
+
+from fastapi import WebSocket
+
+
+@dataclass
+class ClientConnection:
+    websocket: WebSocket
+    client_id: str
+
+
+class ConnectionManager:
+    def __init__(self):
+        self.active_connections: dict[str, list[ClientConnection]] = {}
+
+    async def connect(self, websocket: WebSocket, room_id: str, client_id: str):
+        await websocket.accept()
+        self.active_connections.setdefault(room_id, [])
+        self.active_connections[room_id].append(
+            ClientConnection(websocket=websocket, client_id=client_id)
+        )
+
+    def disconnect(self, websocket: WebSocket, room_id: str):
+        if room_id not in self.active_connections:
+            return
+
+        self.active_connections[room_id] = [
+            connection
+            for connection in self.active_connections[room_id]
+            if connection.websocket is not websocket
+        ]
+
+        if not self.active_connections[room_id]:
+            del self.active_connections[room_id]
+
+    async def send_json(self, websocket: WebSocket, payload: dict[str, Any]):
+        await websocket.send_json(payload)
+
+    async def broadcast_json(self, payload: dict[str, Any], room_id: str):
+        if room_id not in self.active_connections:
+            return
+
+        dead_connections: list[WebSocket] = []
+
+        for connection in list(self.active_connections[room_id]):
+            try:
+                await connection.websocket.send_json(payload)
+            except Exception:
+                dead_connections.append(connection.websocket)
+
+        for websocket in dead_connections:
+            self.disconnect(websocket, room_id)
+
+    def room_users(self, room_id: str) -> list[str]:
+        return [
+            connection.client_id
+            for connection in self.active_connections.get(room_id, [])
+        ]
+
+    def rooms_overview(self) -> dict[str, Any]:
+        return {
+            "rooms": [
+                {
+                    "room_id": room_id,
+                    "online_count": len(connections),
+                    "users": [connection.client_id for connection in connections],
+                }
+                for room_id, connections in self.active_connections.items()
+            ]
+        }
+
+
+manager = ConnectionManager()