Hi Jefferson,

I'm assuming you mean in a web/mobile app?

That being the case on the client you can see what the current rowid is for a cursor.

var csr = Lianja.getCursor("attachments")
Lianja.evaluate(format("sendAttachment('{0}', '{1}', '{2}', {3})", Lianja.App.database, csr.table, 'attachmentcolumn', csr.rowid));

The sendAttachment() server side proc can just extract the attachment into an external file using objectWrite()

Then use the networkrequest class postFile() method.
https://www.lianja.com/doc/index.php/NetworkRequest