@Test
  public void receiveBigResponse() {
    int locatorPort = createLocator(getVM(0));
    for (int i = 1; i <= NUM_SERVERS; i++) {
      createCacheAndRegion(getVM(i), locatorPort);
    }
    DistributedMember vm2ID =
        getVM(2).invoke(() -> cache.getDistributedSystem().getDistributedMember());
    getVM(1).invoke("receive a large direct-reply message", () -> {
      SerialAckedMessageWithBigReply messageWithBigReply = new SerialAckedMessageWithBigReply();
      await().until(() -> {
        messageWithBigReply.send(Collections.singleton(vm2ID));
        return true;
      });
    });
  }
This class tests cluster tcp/ip communications both with and without SSL enabled
geode-core/src/upgradeTest/java/org/apache/geode/ClusterCommunicationsDUnitTest.java