public synchronized void newClient(String update) {
        String newaddress = update;
        if (update.charAt(0) == 'A') {newaddress = update.substring(1);}
        if (addresses.add(newaddress)) {
            for (String a: addresses) {
                if (!output.contains("A" + a)){
                    try {
                        output.put("A" + a);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }