private OptionalInt getDiscPortQueryParam() {
    final int listeningPort = getListeningPortOrZero();
    final int discoveryPort = getDiscoveryPortOrZero();
    if (listeningPort == discoveryPort) {
      return OptionalInt.empty();
    }
    return OptionalInt.of(discoveryPort);
  }
Returns the discovery port only if it differs from the listening port

@return The port, as an optional.
ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/peers/EnodeURLImpl.java