Loading data files from a local machine rather than the server when using gsql_client.jar

When using the remote GSQL client (gsql_client.jar), users appear to only be allowed to load files from the server rather than from the local machine.

Is there a way to load files locally, from a URL, or from other sources? It would be helpful, especially for testing, to be able to load files directly from a local machine or from a URL. Is there something I am missing?