code: public ZAuth allow(String address)
      {
          Objects.requireNonNull(address, "Address has to be supplied for allowance");
          return send(ALLOW, address);
      }
docs: Allow (whitelist) a single IP address. For NULL, all clients from this
  address will be accepted. For PLAIN and CURVE, they will be allowed to
  continue with authentication. You can call this method multiple times to
  whitelist multiple IP addresses. If you whitelist a single address, any
  non-whitelisted addresses are treated as blacklisted.
  @param address