public void endAudioChat(String chat){
        AudioThread thread = audioRooms.get(chat);
        if (thread==null) return;
        Scanner scanner = new Scanner(chat); String sender = scanner.next(); String target = scanner.next();
        ChatServerThread senderThread = users.get(sender).getThread(); if (senderThread!=null) senderThread.send("/decline"); //to tell the client to stop the chat
        ChatServerThread targetThread = users.get(sender).getThread(); if (targetThread!=null) targetThread.send("/decline"); //to tell the client to stop the chat
        thread.stopRunning();
    }