vtkSMReaderFactory::TestFileReadability 

bool vtkSMReaderFactory::TestFileReadability(const char* filename, vtkSMSession* session)
{
  assert("Session should be valid" && session);
  vtkSMSessionProxyManager* pxm =
    vtkSMProxyManager::GetProxyManager()->GetSessionProxyManager(session);
  vtkSmartPointer<vtkSMProxy> proxy;
  proxy.TakeReference(pxm->NewProxy("file_listing", "ServerFileListing"));
  if (!proxy)
  {
    vtkGenericWarningMacro("Failed to create ServerFileListing proxy.");
    return false;
  }

  proxy->SetLocation(vtkProcessModule::DATA_SERVER_ROOT);
  vtkSMPropertyHelper(proxy, "ActiveFileName").Set(filename);
  proxy->UpdateVTKObjects();
  proxy->UpdatePropertyInformation();

  if (vtkSMPropertyHelper(proxy, "ActiveFileIsReadable").GetAsInt() != 0)
  {
    return true;
  }

  return false;
}

 proxy->SetLocation(vtkProcessModule::DATA_SERVER_ROOT);

DATA_SERVER_ROOT定义如下：

  /**
   * These flags are used to specify destination servers for the
   * SendStream function.
   * FIXME: These flags should simply move to PVSession. They don't make sense
   * in non-PVSessions since the processes may have different roles in that
   * case.
   */
  enum ServerFlags
  {
    DATA_SERVER = 0x01,
    DATA_SERVER_ROOT = 0x02,
    RENDER_SERVER = 0x04,
    RENDER_SERVER_ROOT = 0x08,
    SERVERS = DATA_SERVER | RENDER_SERVER,
    CLIENT = 0x10,
    CLIENT_AND_SERVERS = DATA_SERVER | CLIENT | RENDER_SERVER
  };

ServerFlags这些标志用于指定SendStream函数的目标服务器。

vtkProcessModule：