public Builder listeningPort(final Optional<Integer> maybeListeningPort) {
      this.listeningPort = maybeListeningPort.filter(port -> port != 0);
      return this;
    }
An optional listening port value. If the value is empty of equal to 0, the listening port
will be empty - indicating the corresponding node is not listening.

@param maybeListeningPort If non-empty represents the port to listen on, if empty means the
    node is not listening
@return The modified builder
ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/peers/EnodeURLImpl.java