@Override
  public void writeEssentialData(DataOutput out,
      SerializationContext context) throws IOException {
    VersioningIO.writeOrdinal(out, getVersionOrdinal(), true);

    int flags = 0;
    if (networkPartitionDetectionEnabled) {
      flags |= NPD_ENABLED_BIT;
    }
    if (preferredForCoordinator) {
      flags |= COORD_ENABLED_BIT;
    }
    out.writeShort(flags);

    StaticSerialization.writeInetAddress(inetAddr, out);
    out.writeInt(udpPort);
    out.writeInt(vmViewId);
    out.writeLong(uuidMSBs);
    out.writeLong(uuidLSBs);
    if (context.getSerializationVersion().ordinal() >= KnownVersion.GEODE_1_2_0.ordinal()) {
      out.writeByte(vmKind);
    }
  }
checks to see if this address has UUID information needed to send messages via JGroups
geode-membership/src/main/java/org/apache/geode/distributed/internal/membership/gms/GMSMemberData.java