public Builder discoveryPort(final int discoveryPort) {
      return discoveryPort(Optional.of(discoveryPort));
    }
The port on which to listen for discovery messages. A value that is equal to 0, indicates
that the node is not listening for discovery messages.

@param discoveryPort If 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