diff --git a/.gitignore b/.gitignore
index f8b73e7..29dba5a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -137,4 +137,3 @@ dmypy.json
 
 # Cython debug symbols
 cython_debug/
-
diff --git a/setup.cfg b/setup.cfg
index bbe0b4e..0baf1c8 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -8,7 +8,7 @@ url = https://gitea.auro.re/histausse/matrix-bot
 
 [options]
 packages = matrix_bot
-python_requires = >=3.6
+python_requires = >=3.9.2
 package_dir = =src
 install_requires = 
 		matrix-nio>=0.18.7
diff --git a/src/matrix_bot/client.py b/src/matrix_bot/client.py
index 6e8afe8..7fdd26d 100644
--- a/src/matrix_bot/client.py
+++ b/src/matrix_bot/client.py
@@ -3,10 +3,85 @@ The Client class.
 Connect to the matrix server and handle interactions with the server.
 """
 
+import asyncio
+import nio
+from typing import (
+    Optional,
+    NoReturn,
+    Union
+)
+from .utils import (
+    Room,
+    RoomAlias,
+    RoomId
+)
 
 class Client:
     """
         Connect to the matrix server and handle interactions with the
         server.
+
+        allowed_rooms: dict of the rooms where the bot is allowed to connect, indexed
+            by id (the name starting with '!'). If set to None, the bot connect to
+            all room where it is invited.
     """
-    pass
+
+    __client: nio.AsyncClient
+    allowed_rooms: Optional[dict[RoomId, Room]]
+
+    def __init__(
+        self,
+        username: str,
+        homeserver: str,
+        password: str,
+        allowed_rooms_names: Optional[list[Union[RoomAlias, RoomId]]]=None
+    ):
+        """
+            Initialize the Client.
+            username: the username used by the bot
+            homeserver: the matrix home server of the bot (expl: "https://matrix.org")
+            password: the password of the user
+            allowed_rooms: the list of the rooms where the bot is allowed to connect
+                (given by room id (expl: '!xxx:matrix.org') of room alias (expl:
+                '#xxx:matrix.org'))
+        """
+        loop = asyncio.get_event_loop()
+        self.__client = nio.AsyncClient(
+            homeserver,
+            username
+        )
+        resp = loop.run_until_complete(self.__client.login(password))
+        if isinstance(resp, nio.responses.LoginError):
+            raise RuntimeError(f"Fail to connect: {resp.message}")
+
+        # Where is the async map when you need it?
+        self.allowed_rooms = None
+        if allowed_rooms_names:
+            self.allowed_rooms = {}
+            for room_name in allowed_rooms_names:
+                room = loop.run_until_complete(self.resolve_room(room_name))
+                if room.id in self.allowed_rooms:
+                    self.allowed_rooms[room.id].aliases.update(room.aliases)
+                else:
+                    self.allowed_rooms[room.id] = room
+
+
+    async def resolve_room(
+        self,
+        room_name: Union[RoomAlias, RoomId]
+    )->Room:
+        """
+            Lookup a room from its id or alias.
+        """
+        if len(room_name) == 0:
+            raise ValueError(f"Invalid room_name: {room_name}")
+        if room_name[0] == '!':
+            return Room(id=room_name)
+        elif room_name[0] != '#':
+            raise ValueError(f"Invalid room_name: {room_name}")
+        else:
+            resp = await self.__client.room_resolve_alias(room_name)
+            if isinstance(resp, nio.responses.RoomResolveAliasError):
+                raise RuntimeError(f"Error while resolving alias: {resp.message}")
+            return Room(id=resp.room_id,aliases={room_name})
+
diff --git a/src/matrix_bot/utils.py b/src/matrix_bot/utils.py
new file mode 100644
index 0000000..15e7a4e
--- /dev/null
+++ b/src/matrix_bot/utils.py
@@ -0,0 +1,19 @@
+"""
+Utilities for the bot.
+"""
+
+from dataclasses import (
+    dataclass,
+    field
+)
+
+RoomAlias = str
+RoomId = str
+
+@dataclass
+class Room:
+    """ Class representing a room.
+    """
+    id: RoomId
+    aliases: set[RoomAlias] = field(default_factory=set)
+
diff --git a/tests/test.py b/tests/test.py
new file mode 100644
index 0000000..7222d4c
--- /dev/null
+++ b/tests/test.py
@@ -0,0 +1,19 @@
+"""
+Not really tests, because I don't know how to testt without a whole matrix server.
+"""
+
+import os
+from dotenv import load_dotenv
+from matrix_bot.client import Client
+from getpass import getpass
+
+if __name__ == "__main__":
+    load_dotenv()
+    client = Client(
+        os.environ["MUSER"],
+        os.environ["HOMESERVER"],
+        os.environ["PASSWD"],
+        os.environ["ROOMS"].split(",")
+    )
+    print(client.allowed_rooms)
+