code: public InetAddress getInetAddress() throws UnknownHostException{
       if(ip!=null) return ip;
  
       return (ip=InetAddress.getByName(host));
     }
docs: Returns IP field of the message as IP, if the message was created
  with ATYP of HOSTNAME, it will attempt to resolve the hostname,
  which might fail.
  @throws UnknownHostException if host can't be resolved.