public void pongReceived(Address sender) {
      logger.info("received ping-pong response from {}", sender);
      JGAddress jgSender = (JGAddress) sender;
      SocketAddress sockaddr = new InetSocketAddress(jgSender.getInetAddress(), jgSender.getPort());
      ID memberAddr = addressConversionMap.get(sockaddr);

      if (memberAddr != null) {
        logger.info("quorum check: mapped address to member ID {}", memberAddr);
        receivedAcks.add(memberAddr);
      }
    }
GMSQuorumChecker is the implementation of QuorumChecker and can be used to determine
whether a quorum of membership is accessible.
geode-membership/src/main/java/org/apache/geode/distributed/internal/membership/gms/messenger/GMSQuorumChecker.java