code: public List<ContactTokenDetails> getContacts(Set<String> e164numbers)
        throws IOException
    {
      Map<String, String>       contactTokensMap = createDirectoryServerTokenMap(e164numbers);
      List<ContactTokenDetails> activeTokens     = this.pushServiceSocket.retrieveDirectory(contactTokensMap.keySet());
  
      for (ContactTokenDetails activeToken : activeTokens) {
        activeToken.setNumber(contactTokensMap.get(activeToken.getToken()));
      }
  
      return activeTokens;
    }
docs: Checks which contacts in a set are registered with the server.
  
  @param e164numbers The contacts to check.
  @return A list of ContactTokenDetails for the registered users.
  @throws IOException