diff --git a/client/brewpi_gui.py b/client/brewpi_gui.py
index c093c28..8805b6b 100755
--- a/client/brewpi_gui.py
+++ b/client/brewpi_gui.py
@@ -160,7 +160,9 @@ class Window(QtWidgets.QMainWindow, Ui_MainWindow):
 		loop = asyncio.new_event_loop()
 		asyncio.set_event_loop(loop)
 		self.msg_dispatch = MessageDispatcherSync(auto_subscribe=True)
+		self.msg_dispatch.on_connect_changed = self.on_ws_connect_changed
 		self.ws_client = WsClient(listener=self.msg_dispatch, loop=loop)
+		self.connected = False
 		self.msg_pot = self.msg_dispatch.msgio_get('Pot')
 		self.msg_sensor = self.msg_dispatch.msgio_get('Sensor')
 		self.msg_heater = self.msg_dispatch.msgio_get('Heater')
@@ -176,7 +178,7 @@ class Window(QtWidgets.QMainWindow, Ui_MainWindow):
 		self.msg_sud.set_recv_handler(self.on_sud_changed)
 
 		self.setupUi(self)
-		self.btn_connect.clicked.connect(self.connect)
+		self.btn_connect.clicked.connect(self.on_btn_connect_clicked)
 		self.actionStop.triggered.connect(self.disconnect)
 		self.actionSudDownload.triggered.connect(self.on_action_sud_download)
 		self.actionSudUpload.triggered.connect(self.on_action_sud_upload)
@@ -246,6 +248,16 @@ class Window(QtWidgets.QMainWindow, Ui_MainWindow):
 	def disconnect(self):
 		self.ws_client.disconnect()
 
+	def on_btn_connect_clicked(self):
+		if self.connected:
+			self.disconnect()
+		else:
+			self.connect()
+
+	def on_ws_connect_changed(self, connected):
+		self.connected = connected
+		self.btn_connect.setText("Disconnect" if connected else "Connect")
+
 	def on_slider_temp_soll_changed(self, value):
 		print("on_slider_temp_soll_changed {}".format(value))
 		self.msg_tempctrl.send({'Soll': {'Temp': value}})
diff --git a/ws/message.py b/ws/message.py
index 2299a32..dd978ac 100644
--- a/ws/message.py
+++ b/ws/message.py
@@ -103,6 +103,10 @@ class MessageDispatcherSync(IConnection):
 		self.state = None
 		self.state = queue.Queue()
 		self.auto_subscribe = auto_subscribe
+		# Optional callback(connected: bool), invoked from the websocket
+		# client's background thread/loop - e.g. for a GUI to toggle a
+		# Connect/Disconnect button once the connection is actually live.
+		self.on_connect_changed = None
 
 	def msgio_get(self, key):
 		obj = MsgIoSync(key, self.send)
@@ -114,6 +118,8 @@ class MessageDispatcherSync(IConnection):
 	async def on_connect(self):
 		if self.auto_subscribe:
 			asyncio.get_event_loop().run_in_executor(None, self.subscribe)
+		if self.on_connect_changed is not None:
+			self.on_connect_changed(True)
 
 	def subscribe(self):
 		for handler in self.msg_handlers:
@@ -122,7 +128,8 @@ class MessageDispatcherSync(IConnection):
 			self.send({'+': key})
 
 	async def on_disconnect(self):
-		pass
+		if self.on_connect_changed is not None:
+			self.on_connect_changed(False)
 
 	async def on_recv(self, data):
 		d = json.loads(data)