code: public String getPeerInternalHostName (String nodeName)
      {
          if (Objects.equal(_nodeName, nodeName)) {
              return _self.hostName;
          }
          PeerNode peer = _peers.get(nodeName);
          return (peer == null) ? null : peer.getInternalHostName();
      }
docs: Returns the internal hostname to use when connecting to the specified peer or null if the
  peer is not currently connected to this server. Peers connect to one another via their
  internal hostname. Do not publish this data to clients out on the Internets.