int readMcastPort() {
    int result = 0;
    if (optionalFields != null) {
      String resultString = optionalFields.getProperty(MCAST_PORT);
      if (resultString != null && !resultString.isEmpty()) {
        result = Integer.parseInt(resultString);
      }
    }
    return result;
  }
Write the value for the optional field {@link #HOSTED_LOCATORS}.
geode-core/src/main/java/org/apache/geode/distributed/internal/StartupMessageData.java