static Optional<Integer> initTCP(final Map<String, Bytes> data) {
    var tcpBytes = data.get("tcp");
    return tcpBytes != null ? Optional.of(tcpBytes.toInt()) : Optional.empty();
  }
The TCP port of the ENR

@return the TCP port associated with this ENR
ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/discovery/dns/EthereumNodeRecord.java