code: public Optional<ContactTokenDetails> getContact(String e164number) throws IOException {
      String              contactToken        = createDirectoryServerToken(e164number, true);
      ContactTokenDetails contactTokenDetails = this.pushServiceSocket.getContactTokenDetails(contactToken);
  
      if (contactTokenDetails != null) {
        contactTokenDetails.setNumber(e164number);
      }
  
      return Optional.fromNullable(contactTokenDetails);
    }
docs: Checks whether a contact is currently registered with the server.
  
  @param e164number The contact to check.
  @return An optional ContactTokenDetails, present if registered, absent if not.
  @throws IOException