You can also call this utility from the command line. For example, using curl to upload a file "file.xls":
curl -F "f=@file.xls" https://jansson.net/apps/dataupload/
To upload two (or more) files, use the array syntax like in PHP:
curl -F "f[]=@file1.xls" -F "f[]=@file2.xls" https://jansson.net/apps/dataupload/