bugfix chat distribution

server.py

@@ -624,8 +624,9 @@ class Server(multiprocessing.Process):
         for key in self.local_clients_cache:
             if group in key:
                 if addr[0] != self.local_clients_cache[key][0]:
-                    receiver_list.append(self.local_clients_cache[key][0])
-                    print(self.server_id+": "+"Group receiver list "+str(receiver_list))
+                    if self.local_clients_cache[key][0] not in receiver_list:
+                        receiver_list.append(self.local_clients_cache[key][0])
+                        print(self.server_id+": "+"Group receiver list "+str(receiver_list))
                 elif addr[0] == self.local_clients_cache[key][0]:
                     sender = key