protected Integer createServer(final VM vm) {
    return vm.invoke(() -> {
      CacheServer server = getCache().addCacheServer();
      server.setPort(0);
      server.start();
      return server.getPort();
    });
  }
Base class for function tests that use client server. This class takes care of setting up the
client server topology.
geode-core/src/distributedTest/java/org/apache/geode/internal/cache/execute/FunctionServiceClientBase.java