@BeforeClass
  public static void setup() {
    DUnitLauncher.launchIfNeeded(NUM_SERVERS + 1);
    invokeInEveryVM(
        () -> InternalDataSerializer.getDSFIDSerializer().register(
            SerialAckedMessageWithBigReply.DSFID,
            SerialAckedMessageWithBigReply.class));
  }
This class tests cluster tcp/ip communications both with and without SSL enabled
geode-core/src/upgradeTest/java/org/apache/geode/ClusterCommunicationsDUnitTest.java