Transferring data from client side desktop app to server side web app

I have a desktop application on the client side which will be calling my web app on the server by a click of a button on the desktop app. But I want to transfer some data from that data and populate that data on to the web app which is on the server. I don't want to go with the approach of adding the data as part of the URL because it will be very long and there might be sensitive data. Is there anyway of transferring the data from the desktop app to the web app.