private boolean isRegisteredUser(String candidName, DataOutputStream outToClient) throws IOException {

        String userName = client.getUser();
        logfile.update("Client: " + candidName);

        String[] request = candidName.trim().split(" ");

        //if one word: expected NOOP or QUIT or something else
        if (request.length == 1) {
            if (request[0].startsWith("NOOP")) {
                send(outToClient, " +OK");
            } else if (request[0].startsWith("QUIT")) {
                this.close();
            } else {
                send(outToClient, "-ERR Unknown command - 1");
            }
        }

        //if two word: expected USER + username or something else
        if (request.length == 2) {
            if (!request[0].startsWith("USER")) {
                send(outToClient, "-ERR Unknown command - 2");
            } else if (request[1].startsWith(userName)) {
                send(outToClient, "+OK " + request[1] + " is a real user");
                return true;
            } else {
                send(outToClient, "-ERR Unknow user");
            }
        }

        //if more as two word: not accept
        if (request.length > 2) send(outToClient, "-ERR Unknown comman - 3");

        return false;
    }