refactor: use websocket again

listener_counter.py

@@ -0,0 +1,19 @@
+import threading
+
+
+class ListenerCounter:
+    def __init__(self) -> None:
+        self.__listener = set()
+        self.__lock = threading.Lock()
+
+    def add_listener(self, listener_id: str):
+        with self.__lock:
+            self.__listener.add(listener_id)
+
+    def remove_listener(self, listener_id: str):
+        with self.__lock:
+            self.__listener.discard(listener_id)
+
+    def count(self) -> int:
+        with self.__lock:
+            return len(self.__listener)