private static String createClientMessagesRegion(InternalRegionFactory factory, int port) {
    // generating unique name in VM for ClientMessagesRegion
    String regionName = generateNameForClientMsgsRegion(port);
    try {
      factory.setDestroyLockFlag(true).setRecreateFlag(false)
          .setSnapshotInputStream(null).setImageTarget(null).setIsUsedForMetaRegion(true);
      factory.create(regionName);
    } catch (RegionExistsException ree) {
      InternalGemFireError assErr = new InternalGemFireError("unexpected exception", ree);
      throw assErr;
    }
    return regionName;
  }
create client subscription

@return client subscription name
@since GemFire 5.7
geode-core/src/main/java/org/apache/geode/internal/cache/CacheServerImpl.java