public Builder discoveryPort(final Optional<Integer> maybeDiscoveryPort) {
      this.discoveryPort = maybeDiscoveryPort.filter(port -> port != 0);
      return this;
    }
The port on which to listen for discovery messages. A value that is empty or equal to 0,
indicates that the node is not listening for discovery messages.

@param maybeDiscoveryPort If non-empty and non-zero, represents the port on which to listen
    for discovery messages. Otherwise, indicates that the node is not running discovery.
@return The modified builder
ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/peers/EnodeURLImpl.java