diff --git a/src/app/store.ts b/src/app/store.ts
index 5eecac9..5b6ddb9 100644
--- a/src/app/store.ts
+++ b/src/app/store.ts
@@ -1,4 +1,9 @@
-import { configureStore, ThunkAction, Action } from "@reduxjs/toolkit";
+import {
+  combineReducers,
+  configureStore,
+  ThunkAction,
+  Action,
+} from "@reduxjs/toolkit";
 
 import counterReducer from "../features/counter/counterSlice";
 // TODO: Rework these to use a slice, otherwise redux complains about
@@ -13,14 +18,22 @@ import roomReducer from "../modules/room/slice";
 import makeSocketMiddleware from "../modules/websocket/middleware";
 import socketReducer from "../modules/websocket/slice";
 
+const rootReducer = combineReducers({
+  counter: counterReducer,
+  login: loginReducer,
+  rooms: roomReducer,
+  socket: socketReducer,
+  //users,
+});
+
+// Define this before defining `store`, to break a circular type reference:
+//
+//   store -> middleware -> RootState
+//
+export type RootState = ReturnType<typeof rootReducer>;
+
 export const store = configureStore({
-  reducer: {
-    counter: counterReducer,
-    login: loginReducer,
-    rooms: roomReducer,
-    socket: socketReducer,
-    //users,
-  },
+  reducer: rootReducer,
   middleware: (getDefaultMiddleware) =>
     getDefaultMiddleware().concat(
       makeSocketMiddleware(loginSocketMessageHandlers)
@@ -28,7 +41,6 @@ export const store = configureStore({
 });
 
 export type AppDispatch = typeof store.dispatch;
-export type RootState = ReturnType<typeof store.getState>;
 export type AppThunk<ReturnType = void> = ThunkAction<
   ReturnType,
   RootState,
diff --git a/src/components/ConnectForm.tsx b/src/components/ConnectForm.tsx
index 1b8d34a..2fa5d89 100644
--- a/src/components/ConnectForm.tsx
+++ b/src/components/ConnectForm.tsx
@@ -17,7 +17,7 @@ interface Props {
 const ConnectForm: FC<Props> = ({ socket }) => {
   const dispatch = useDispatch();
 
-  const onSubmit = ({ url }) => {
+  const onSubmit = ({ url }: { url: string }) => {
     dispatch(socketOpen(url));
   };
 
diff --git a/src/components/Header.tsx b/src/components/Header.tsx
index ac7df07..0cb2fca 100644
--- a/src/components/Header.tsx
+++ b/src/components/Header.tsx
@@ -1,15 +1,15 @@
 import { FC } from "react";
-import { Link } from "react-router-dom";
+import { NavLink } from "react-router-dom";
 
 const Header: FC = () => (
   <header>
     <h1>Solstice web UI</h1>
-    <Link to="/rooms" activeClassName="active">
+    <NavLink to="/rooms" activeClassName="active">
       Rooms
-    </Link>
-    <Link to="/users" activeClassName="active">
+    </NavLink>
+    <NavLink to="/users" activeClassName="active">
       Users
-    </Link>
+    </NavLink>
   </header>
 );
 
diff --git a/src/components/RoomList.tsx b/src/components/RoomList.tsx
index ef92822..9245f03 100644
--- a/src/components/RoomList.tsx
+++ b/src/components/RoomList.tsx
@@ -3,9 +3,11 @@ import { useDispatch } from "react-redux";
 
 import RoomComponent from "./Room";
 import SearchableList from "./SearchableList";
-import { Room, RoomSliceState } from "../modules/room/slice";
+import { RoomSliceState } from "../modules/room/slice";
 import { socketSendMessage } from "../modules/websocket/slice";
 
+const SearchableRoomList = SearchableList(RoomComponent);
+
 const RoomList: FC<RoomSliceState> = ({ rooms }) => {
   const dispatch = useDispatch();
   const refresh = () => {
@@ -17,13 +19,7 @@ const RoomList: FC<RoomSliceState> = ({ rooms }) => {
     );
   };
 
-  return (
-    <SearchableList<Room, RoomComponent>
-      id="room-list"
-      map={rooms}
-      refresh={refresh}
-    />
-  );
+  return <SearchableRoomList id="room-list" map={rooms} refresh={refresh} />;
 };
 
 export default RoomList;
diff --git a/src/components/SearchableList.tsx b/src/components/SearchableList.tsx
index 7e9a1ab..974e9e1 100644
--- a/src/components/SearchableList.tsx
+++ b/src/components/SearchableList.tsx
@@ -1,43 +1,46 @@
-import { ComponentType, FC } from "react";
+import { ComponentType, FC, ReactEventHandler } from "react";
 
-interface Props<Item> {
+interface ItemProps<Item> {
+  name: string;
+  data: Item;
+}
+
+interface ListProps<Item> {
   id: string;
   map: { [key: string]: Item };
   refresh: () => void;
 }
 
-function SearchableList<
-  Item,
-  ItemComponent extends ComponentType<Props<Item>>
->({ id, map, refresh }: Props<Item>) {
-  const children = [];
+function SearchableList<Item>(
+  ItemComponent: ComponentType<ItemProps<Item>>
+): FC<ListProps<Item>> {
+  return ({ id, map, refresh }: ListProps<Item>) => {
+    const children = [];
 
-  for (const name in map) {
-    children.push(
-      <li key={name}>
-        <ItemComponent name={name} data={map[name]} />
-      </li>
-    );
-  }
+    for (const name in map) {
+      children.push(
+        <li key={name}>
+          <ItemComponent name={name} data={map[name]} />
+        </li>
+      );
+    }
 
-  const onClick = (event) => {
-    event.preventDefault();
-    refresh();
-  };
+    const onClick: ReactEventHandler = (event) => {
+      event.preventDefault();
+      refresh();
+    };
 
-  return (
-    <div id={id}>
-      <div id={`${id}-header`}>
-        <div>
-          <button onClick={onClick}>Refresh</button>
+    return (
+      <div id={id}>
+        <div id={`${id}-header`}>
+          <div>
+            <button onClick={onClick}>Refresh</button>
+          </div>
         </div>
+        <ul>{children}</ul>
       </div>
-      <ul>{children}</ul>
-    </div>
-  );
+    );
+  };
 }
 
-// eslint-disable-next-line
-let _assertType: FC<Props<Item>> = SearchableList;
-
 export default SearchableList;
diff --git a/src/components/SolsticeApp.tsx b/src/components/SolsticeApp.tsx
index 91b4951..91cd373 100644
--- a/src/components/SolsticeApp.tsx
+++ b/src/components/SolsticeApp.tsx
@@ -44,7 +44,8 @@ const ConnectedApp: FC = ({ children }) => {
     );
   }
 
-  return children;
+  // TODO: eliminate the need for this extra <div> wrapper.
+  return <div>{children}</div>;
 };
 
 const SolsticeApp = () => (
diff --git a/src/modules/login/message.ts b/src/modules/login/message.ts
index 1848bc1..736a07c 100644
--- a/src/modules/login/message.ts
+++ b/src/modules/login/message.ts
@@ -1,5 +1,5 @@
-import { loginSetState } from "../login/slice";
-import { SocketMessage } from "../websocket/message";
+import { loginSetState, LoginStatus } from "../login/slice";
+import { SocketMessage, SocketMessageHandler } from "../websocket/message";
 
 export function loginStatusRequest(): SocketMessage {
   return {
@@ -21,7 +21,7 @@ const loginStatusResponseHandler: SocketMessageHandler = {
         });
       }
       case "Success": {
-        const [username, motd] = data.fields;
+        const [username, motd] = fields;
         return loginSetState({
           status: LoginStatus.Success,
           username,
@@ -30,7 +30,7 @@ const loginStatusResponseHandler: SocketMessageHandler = {
       }
 
       case "Failure": {
-        const [username, reason] = data.fields;
+        const [username, reason] = fields;
         return loginSetState({
           status: LoginStatus.Failure,
           username,
diff --git a/src/modules/login/slice.ts b/src/modules/login/slice.ts
index 9a1c6af..9107da3 100644
--- a/src/modules/login/slice.ts
+++ b/src/modules/login/slice.ts
@@ -19,9 +19,6 @@ export interface LoginSliceState {
 
 const initialState: LoginSliceState = {
   status: LoginStatus.Unknown,
-  url: undefined,
-  motd: undefined,
-  reason: undefined,
 };
 
 export const loginSlice = createSlice({
@@ -29,7 +26,7 @@ export const loginSlice = createSlice({
   initialState,
   reducers: {
     loginSetState: (
-      state: RootState,
+      state: LoginSliceState,
       action: PayloadAction<LoginSliceState>
     ) => {
       state = action.payload;
diff --git a/src/modules/room/slice.ts b/src/modules/room/slice.ts
index a7db6e0..dc2fb8f 100644
--- a/src/modules/room/slice.ts
+++ b/src/modules/room/slice.ts
@@ -9,6 +9,11 @@ export enum RoomMembership {
   Left,
 }
 
+export interface RoomMessage {
+  user_name: string;
+  message: string;
+}
+
 export interface Room {
   name: string;
   membership: RoomMembership;
@@ -18,18 +23,24 @@ export interface Room {
   owner: string;
   operators: Set<string>;
   members: Set<string>;
-  messages: string[];
+  messages: RoomMessage[];
   tickers: string[];
   // showUsers: boolean;
 }
 
-export interface RoomSliceState {
+export interface RoomMap {
   [name: string]: Room;
 }
 
-const initialState: RoomSliceState = {};
+export interface RoomSliceState {
+  rooms: RoomMap;
+}
 
-export interface RoomMessage {
+const initialState: RoomSliceState = {
+  rooms: {},
+};
+
+export interface RoomMessagePayload {
   room_name: string;
   user_name: string;
   message: string;
@@ -44,7 +55,7 @@ export const roomSlice = createSlice({
       action: PayloadAction<[string, RoomMembership]>
     ) => {
       const [name, membership] = action.payload;
-      const room = state[name];
+      const room = state.rooms[name];
       if (room === undefined) {
         console.log(`Cannot set membership of room ${name}`);
         return;
@@ -54,10 +65,10 @@ export const roomSlice = createSlice({
     },
     roomMessage: (
       state: RoomSliceState,
-      action: PayloadAction<RoomMessage>
+      action: PayloadAction<RoomMessagePayload>
     ) => {
       const { room_name, user_name, message } = action.payload;
-      const room = state[room_name];
+      const room = state.rooms[room_name];
       if (room === undefined) {
         console.log(
           `Unknown room ${room_name} received message from ` +
@@ -71,7 +82,7 @@ export const roomSlice = createSlice({
     roomSetAll: (state: RoomSliceState, action: PayloadAction<Room[]>) => {
       state.rooms = {};
       for (const room of action.payload) {
-        state[room.name] = room;
+        state.rooms[room.name] = room;
       }
     },
   },
@@ -79,9 +90,8 @@ export const roomSlice = createSlice({
 
 export const { roomSetMembership, roomMessage, roomSetAll } = roomSlice.actions;
 
-export const selectAllRooms = (state: RootState) => state.rooms.rooms;
-
-export const selectRoom = (name: string) => (state: RootState) =>
-  state.rooms.rooms.get(name);
+export function selectAllRooms(state: RootState): RoomMap {
+  return state.rooms.rooms;
+}
 
 export default roomSlice.reducer;
diff --git a/src/modules/websocket/actions.ts b/src/modules/websocket/actions.ts
deleted file mode 100644
index eb33ce7..0000000
--- a/src/modules/websocket/actions.ts
+++ /dev/null
@@ -1,5 +0,0 @@
-export const wsConnect = (host) => ({ type: "WS_CONNECT", host });
-export const wsConnecting = (host) => ({ type: "WS_CONNECTING", host });
-export const wsConnected = (host) => ({ type: "WS_CONNECTED", host });
-export const wsDisconnect = () => ({ type: "WS_DISCONNECT" });
-export const wsDisconnected = () => ({ type: "WS_DISCONNECTED" });
diff --git a/src/modules/websocket/message.ts b/src/modules/websocket/message.ts
index 3162b29..9495aa8 100644
--- a/src/modules/websocket/message.ts
+++ b/src/modules/websocket/message.ts
@@ -5,7 +5,7 @@ import { PayloadAction } from "@reduxjs/toolkit";
 // The type of a message exchanged over a websocket.
 export interface SocketMessage {
   variant: string;
-  fields?: List<any>;
+  fields: any[];
 }
 
 // Serializes the given message for sending over the wire.
@@ -25,7 +25,9 @@ export function parseMessage(serialized: string): SocketMessage {
 }
 
 // Handles the `data` field of a `SocketMessage` and returns an optional action.
-export type SocketMessageDataHandler = (any) => PayloadAction<any> | undefined;
+export type SocketMessageDataHandler = (
+  data: any
+) => PayloadAction<any> | undefined;
 
 // A message handler creates an action out of a socket message.
 //
diff --git a/src/modules/websocket/middleware.ts b/src/modules/websocket/middleware.ts
index 6a762dd..cec4bc4 100644
--- a/src/modules/websocket/middleware.ts
+++ b/src/modules/websocket/middleware.ts
@@ -17,24 +17,24 @@ import {
   socketClosed,
   socketSendMessage,
 } from "./slice";
-import { AppDispatch, RootState } from "../app/store";
+import { AppDispatch, RootState } from "../../app/store";
 
 // The WebSocket singleton.
-// TODO: use undefined instead, it is more idiomatic.
-let socket: WebSocket | null = null;
+let socket: WebSocket | undefined;
 
-const onOpen = (dispatch: AppDispatch) => (event) => {
-  console.log("Websocket open", event.target.url);
-  dispatch(socketOpened(event.target.url));
+const makeOnOpen = (dispatch: AppDispatch) => (event: Event) => {
+  const target = event.target as WebSocket;
+  console.log("WebSocket open", target.url);
+  dispatch(socketOpened(target.url));
 };
 
-const onClose = (dispatch: AppDispatch) => () => {
+const makeOnClose = (dispatch: AppDispatch) => () => {
   dispatch(socketClosed());
 };
 
-function prepareHandlers(
-  handlers: SocketMessageHandler[]
-): Map<string, SocketMessageDataHandler[]> {
+type HandlerMap = Map<string, SocketMessageDataHandler[]>;
+
+function prepareHandlers(handlers: SocketMessageHandler[]): HandlerMap {
   const map = new Map();
 
   for (const handler of handlers) {
@@ -52,16 +52,15 @@ function prepareHandlers(
   return map;
 }
 
-const onMessage =
-  (dispatch: AppDispatch, handlers: Map<string, SocketMessageDataHandler[]>) =>
-  (event: MessageEvent) => {
-    console.log("Websocket received message", event.data);
+const makeOnMessage =
+  (dispatch: AppDispatch, handlers: HandlerMap) => (event: MessageEvent) => {
+    console.log("WebSocket received message", event.data);
 
     let message;
     try {
       message = parseMessage(event.data);
     } catch (err) {
-      console.log("Websocket received invalid message:", err);
+      console.log("WebSocket received invalid message:", err);
       return;
     }
 
@@ -70,7 +69,7 @@ const onMessage =
       return;
     }
 
-    for (handler of list) {
+    for (const handler of list) {
       const action = handler(message);
       if (action !== undefined) {
         dispatch(action);
@@ -78,38 +77,65 @@ const onMessage =
     }
   };
 
+type SocketFactory = (url: string) => WebSocket;
+
+function makeSocketFactory(
+  dispatch: AppDispatch,
+  handlers: HandlerMap
+): SocketFactory {
+  const onOpen = makeOnOpen(dispatch);
+  const onClose = makeOnClose(dispatch);
+  const onMessage = makeOnMessage(dispatch, handlers);
+
+  return (url) => {
+    socket = new WebSocket(url);
+
+    // Bind websocket handlers.
+    socket.onopen = onOpen;
+    socket.onclose = onClose;
+    socket.onmessage = onMessage;
+
+    return socket;
+  };
+}
+
 // See: https://redux.js.org/tutorials/fundamentals/part-4-store#writing-custom-middleware
 function makeMiddleware(
   handlers: SocketMessageHandler[]
 ): Middleware<{}, RootState> {
   const handlerMap = prepareHandlers(handlers);
 
-  return (storeApi) => (next) => (action) => {
-    if (socketOpen.match(action)) {
-      if (socket !== null) {
-        socket.close();
+  return (storeApi) => {
+    const socketFactory = makeSocketFactory(storeApi.dispatch, handlerMap);
+
+    return (next) => (action) => {
+      if (socketOpen.match(action)) {
+        if (socket === undefined) {
+          const url = action.payload;
+          console.log(`Opening WebSocket to ${url}`);
+          socket = socketFactory(url);
+        } else {
+          console.log("Ignoring socketOpen action, socket is already open.");
+        }
+      } else if (socketClose.match(action)) {
+        if (socket !== undefined) {
+          socket.close();
+          socket = undefined;
+          console.log("WebSocket closed.");
+        } else {
+          console.log("Ignoring socketClose action, socket is already closed.");
+        }
+      } else if (socketSendMessage.match(action)) {
+        if (socket !== undefined) {
+          console.log("WebSocket sending message", action.payload);
+          socket.send(JSON.stringify(action.payload));
+        } else {
+          console.log("Ignoring socketSendMessage action, socket is closed.");
+        }
       }
 
-      // Connect to the remote host.
-      socket = new WebSocket(action.payload);
-
-      // Bind websocket handlers.
-      socket.onmessage = onMessage(storeApi.dispatch, handlerMap);
-      socket.onclose = onClose(storeApi.dispatch);
-      socket.onopen = onOpen(storeApi.dispatch);
-    } else if (socketClose.match(action)) {
-      if (socket !== null) {
-        socket.close();
-      }
-
-      socket = null;
-      console.log("Websocket closed.");
-    } else if (socketSendMessage.match(action)) {
-      console.log("Websocket sending message", action.payload);
-      socket.send(JSON.stringify(action.payload));
-    }
-
-    return next(action);
+      return next(action);
+    };
   };
 }
 
diff --git a/src/modules/websocket/slice.ts b/src/modules/websocket/slice.ts
index 0ff6a34..df7208f 100644
--- a/src/modules/websocket/slice.ts
+++ b/src/modules/websocket/slice.ts
@@ -27,7 +27,7 @@ export const socketSlice = createSlice({
       state.state = SocketState.Opening;
       state.url = action.payload;
     },
-    socketOpened: (state, action: PayoadAction<string>) => {
+    socketOpened: (state, action: PayloadAction<string>) => {
       state.state = SocketState.Open;
       state.url = action.payload;
     },