code: public int getPeerPort (String nodeName)
      {
          if (Objects.equal(_nodeName, nodeName)) {
              return _self.port;
          }
          PeerNode peer = _peers.get(nodeName);
          return (peer == null) ? -1 : peer.getPort();
      }
docs: Returns the port on which to connect to the specified peer or -1 if the peer is not
  currently connected to this server.