Null FileStream CSOM

In SharePoint Remote Event Receiver, I'm try to get file stream from a ListItem:

List docs = clientContext.Web.Lists.GetById(listId);
ListItem item = docs.GetItemById(listItemId);
clientContext.Load(item);
clientContext.ExecuteQuery();
var file = item.File.OpenBinaryStream();

But it's returning null, is this limitation in Event Receiver ? I used to use this code in Console, it's working.

Please help to resolve it.