plugins.file.streamFilesToServer

“in the webclient the streaming from the browser to the server is done by the browser”
I am using a webclient. What does this mean I could not use this method to send data from the client to server? If not, can you suggest which is the correct method to use?

no sending data from the browser to the server is done by a fileupload dialog where the user selects a file that it wants to upload
then you get call on the callback method that you give the showFileOpenDialog that gets that file and its content (but then you are already on the server)
The browser does the streaming/upload to the server.